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I have a 55.5 GMC with original 248, my question is, do the Independent Front Suspension kits on the market clear the stock oil pan? To me it looks like it could be a deal breaker since i want to keep the 248. this is the first question of many, but only if the kits work with the straight sixes.

Why replace a full grown truck front suspension system with one for a subcompact car? It's a lot simpler, and probably less expensive to rebuild the straight axle suspension to like new condition. Disc brake kits are available if you want to "upgrade" the brakes to leave longer skid marks in a panic stop situation.
Jerry

Quit poo pooing on the guy’s ideas. This is the HiPo Shop and modifications are welcome stock is not! To the OP, contact the kit manufacturer for each kit you are considering. They all have Tech Support to answer questions such as yours. Good luck

I can answer this one.
Most kits do not have enough clearance. You can modify yourself but you are legally liable if it fails and someone gets hurt.
Manufacturers design kits that go toward the highest sales to keep the costs down.
The majority owners want a Chevy V8 and slam the truck to the ground so this is what is marketed.
If you want the stock inline 6 and somewhat close to stock ride height, you need a rod shop.
Scotts Rod Shop makes these parts but last I heard they only sell to rod shops now. Not to individuals and certainly not me.
I am banned (well politely asked to leave them alone) because I kept asking questions about liability and insurance.

Not sure if this will help, but here is an example in the old Gallery of an IFS set up out of a half-ton GMC that was utilized by "Weeds" in a '49 Suburban.

Weeds 1949 Suburban

John

Titled the Andereggen IFS.
Starting on page 3 (https://www.stovebolt.com/ubbthreads/ubbthreads.php/topics/486622/3.html).
Doing a short recap which may need correction:

The original donor 60's truck IFS track is wider than stock AD truck. The idea was tried then interest fizzled.
Later, after a combination of parts, trial & error and modification to compensate, it looks like a solution was found.
The result is a 60"s truck ride. Some like it and some prefer the MII ride.

It is beyond me how someone such as yourself would have the "gall" to ask a guy a question pertaining to the most common IFS kit out there (Mustang II), regarding whether the guy was aware of exactly what a Mustang II IFS is.
Then you "fly off the handle" by suggesting a simpler, and less expensive option of making what he has as good as new.
Then you "dive into the deep end" and suggest HiPo disc brake upgrade.
In the immortal words of Bugs Bunny, "For shame doc, for shame."
See you in the funny papers...
Carl

Thanks for the responses. I was hoping that someone had done the swap I was contemplating, and I realize that the IFS kits are predominately used for V8 conversions. HRL is correct about rebuilding what I have being a lower cost option, but as far as it being a full grown truck? I was parked next to one yesterday, my 55 looked like a LUV 😁. Doing the IFS opens up a large can of s%$t I'm pretty sure I don't want to open, but doing my research before starting anything. Thanks again ✌

At the end of the day, it boils down to what you want out of the truck when it is done. A 70-ish year old truck drives like one. They were not built for comfort, they were built to work.

If you are wanting to fix it up and use it as a truck (hauling, towing, etc), then going with a lighter weight front suspension will not be the best option. If you are looking for a fun cruiser with modern amenities for carrying half a dozen 2x4s or your cooler to the beach for the day, then it would be just fine and gives you an off-the-shelf path to better suspension, brakes, and steering. The tradeoff is that it will lower your ride. Do you consider that a pro or a con?

Contrary to Hot Rod Lincoln's comment, the Mustang 2 wasn't a subcompact and the kits available today are nothing like what originally came on them other than the basic geometry. That said, they are designed/built for lighter vehicles than a loaded truck. I am assuming you have a 3100 since you don't say and those are the most common. From the GM Heritage documentation, that has a curb weight of 3217lbs compared to a Mustang 2 curb weight of 2822lbs. That is not a huge difference, but it only applies when the truck is *unloaded*. If you put 1500lbs in the back or a trailer behind it, suddenly it is a whole different ballgame.

I looked really strongly at doing the M2 IFS conversion for my 58 and talked to all of the kit manufactures that I could find (POL, Strange, Chassis Engineering, Johnny Law, etc) and found pros/cons to their different offerings. At the end of the whole thing I decided that I still wanted to be able to use my truck to haul a full load of lumber or gravel when it is done, so I am going a different direction with it. I don't think that the IFS is an inherently bad choice, it was just not the right one for me.

Feel free to PM me if you like. Also maybe take a look at Coilover's posts; he has a shop that does a lot of these kind of conversions and has posted some really good info.

There are a number of MII kits available for your truck, some even bolt in. I would contact someone like Speedway and talk with one of their Techs, I'm sure you are not the first to about about leave a 6 cylinder in engine in the truck. Regardless of the kit you decide on there will always be some unknowns. MII IFS usually require use of a rack and pinion which means modifying the steering column, that is just one of many things to consider.

I am in no way trying to dissuade you from using a kit, it will improve the way your truck rides deffintly. Take a look at your options before you cut anything, there is always another way of doing something.

Whoa, whoa, back-up.
rbs56, 55.5 means 55 1/2 or 1955 1st or 1955 first half year or series.
I looked at your profile and you say you have 1955 GMC 100 2nd series.
Big difference in track width. You may be able to do a later year truck IFS parts swap as "J Lucas" mentioned.
Please identify which half year you are asking about.

Lets get something straight here guys. I used to do the same thing. I immediately thought to advise that such and such was dangerous, made no sense, better solutions out there, non stock, screws up a good old truck. We are mostly "original" types here. Maybe a slight brake or lighting or bearing upgrade. But cutting into a frame or tearing out the suspension.....OH NO! Not on Stovebolt. Well..........here is what I think. I have read the description of HiPo shop/Hot Rod Shop. It's advertised as "Thinking about a hotrod, street rod or other custom work? It's not for the AD type, the TF type, originalist, nostalgic or the old design is OK. It's what you call a special forum for HiPo. Ford introduced the "K" code and other High Performance Option choices in about the early 60's. Referred to as HiPo. Now used to describe all kinds of motors and accessories. HiPo Tires, HiPo air fresheners and such. Chevy had HI PERF. Other designations are H.O., SPHP, Z28 and so on.

I've realized that this forum has folks who have already considered doing a custom/radical/deep upgrade for performance reasons, Until they ask if they should do it, we should stick to answering their question. We can go off on someone in the other forums. Repeat, I include myself and past posts.
We probably should not give unsolicited poo pooing advice in this one forum as Martin said. The poster is past the "keep it original/don't screw up a good truck" phase. Usually. They are polite and understanding but they just want the answer from someone who has done the HiPo job....or someone to help research.

It's pretty hard to argue that a 50's straight axle is "better" than Modern IFS in a HiPo build. There are bolt-on IFS for 48 and up Chevy trucks. Obviously designed for whatever load and weight of the truck or liability would be at risk.

They try to cover that by warning that a professional must install it. Even a bolt on! This is so they can blame the owner if they install it or the professional installer. The bottom line is there are no failures that we know of anyway. It's seems like if you can measure stuff and drill some holes, you are in fat city. I have done radical DIY fabrication to TF (55.2-59)

Do what you want. Do something crazy if you want. I do and get some not so friendly comments sometimes. It doesn't even phase me. This forum is my hideout. Just be safe. It's just steel if it doesn't work then you can refine it until you like it. I'm keeping my straight axle and don't know much about this but can you alter the oil pan and maybe move the pickup?

I have known some do it with the chevys and it works but gmc is different because the motor is 1 1/2 longer and it hits the rack even with the small pickup oil pan and as big as the frount main there's not a lot of room to be maid with the oil pan.

[img]https://www.stovebolt.com/ubbthreads/ubbthreads.php/ubb/download/Number/39939/filename/caliper bracket install 1.jpg[/img]Straight axles and leaf springs can be made to perform quite well. The magic is in the shocks. JMHO

This forum is titled the HiPo Shop so why does everything have to fit right out of the box when you are MODIFYING nearly everything. For years I had a sign over my desk that said, "SWAPS!!! We can put a 450 Cummins on a skateboard if you have A: the Cummins B: the skateboard and C: Cash". The so called MII or Pinto IFS units do not remotely resemble the folded tin units used by Ford but are engineered to be as strong as any factory set up. Qualify this to Fatman, Heidts, Chassis Engineering, and several other ENGINEERED units and not ebay specials. The cross members are a full 1/4 inch thick (Fatman) and the A-frames and/or control arms a heavy wall chrome moly. If somehow clamped on one end and pulled/pushed/twisted on the other I'd bet they would out-tough a straight axle. With the right choice of springs they can dependably be used on big block cars. We cut a trough through a Fatman unit to fit a 2004 Mustang Mach1 4 cam engine into a 1950 Ford woody wagon and it is still running trouble free 15 years later. The trough was reboxed for strength but no additional fish plating was used. I realize not everyone has equipment in a home shop to modify to their need but pan clearance to a cross member should not be prohibitively expensive. Think outside the box.

Well, this certainly isn't what I was expecting..... First, sorry that I wasn't more specific on the year, I assumed (I know,don't do that) 55.5 was a standard way of saying second series, my bad. Next, as was stated, I was hoping to hear if anyone had done the swap I proposed. It wasn't something that I had my mind set on, just inquiring. Right now my truck is original except for, 12v conversion, roller bearings on front spindles, LED bulbs, and a 57 Chevy truck rear axle, so I haven't gone down a rabbit hole with it. I also was posting on the Hi-pro page hoping to miss the snarkiness. I do very much appreciate the lively discussion that resulted, but I don't want any bad feelings because of my inquiry. This web site has helped get me through a complete engine rebuild and other projects, so I want to say a big thanks to the stovebolt community, ✌

Good points, Evan. Recently, I bought a very heavy duty IFS system that had been scavenged out of a badly butchered stovebolt frame before the rest of it went to the scrappers. I got it, plus a couple of stock control arms and a rack & pinion steering gear for barely above scrap iron price. It's going to be a good beginning for a non-stovebolt project I'm working on, and it will save me a pile of money compared to building something similar from scratch. I'll modify it to fit my needs. Expecting a perfect fit from any add-on suspension system doesn't make good nonsense, and the people who do that probably don't have any business attempting the project in the first place.

Starting with a pile of steel tubing and ending up with a dirt track race car frame is fun. Those projects will never see a single mile on a public road, however, and the guys who go around in circles and think they're "big wheels" are all out there voluntarily. If something breaks, we hope we're going to survive the crash, and we're going to do it differently the next time. We also have emergency crews available within a few seconds to rescue us. Some of the "resto-mod" vehicles I've done pre-purchase inspections on were in such dangerous shape that I refused to do the road test the assignment required.

I'm all for pushing the envelope, performance-wise. Just don't make the soccer mom with a minivan full of kids the victim of a bad weld or a poorly engineered modification when something breaks.
Jerry

rbs56, I think with a little head scratching and a tape measure you can figure out a work around. You my need to notch the MII crossmember (it's done all the time) or as mick53 suggests modify the oil pan and pickup tube. Both are very doable, with enough research I'm sure you will find someone who has completed this before.

Now a note on why everyone is so against cutting your truck. I don't think anyone is outright against it but doing it correctly and SAFELY is the key point. We all have heard stories about how bad a frame or brake system was butchered, the fear is that another truck will wind up like this. I am currently living the nightmare of undoing some of the very things we are talking about, suspension, brakes, crossmembers and wiring. It really does take the fun out of working on a project when all you do is fix someone else's bad work. (this project is for my BIL, I would not have purchased this truck as soon as I looked under it)

I considered a MII swap and even a subframe clip for my 59', the deciding factor for me was my own abilities. At the time I didn't have the skill set and since then I have learned a lot, would I do it now "YES", but I have so much invested in the parts I have now that it makes no sense.

I say go for it and let everyone else drool, a 6 in a Task Force with a MII IFS, very COOL.

[quote=mick53] This forum is my hideout.

The MII crossmember can be notched. It's actually overbuilt to begin with. If you plan on using a sway bar, you would need to use a front mount one, instead of the rear mount that most MII's use. If you're worried about strength, You can always add and extra gusset.

Most of the MII manufacturers can do a custom crossmember that moves everything down for more clearance. A phone call or two can give you the intel you need. Then there's the universal kit that you cut and notch yourself...

I am installing a Mustang IFS 2 I bought from Tuckers in my 54 Chevy 3100, it's made by CCP. In the instructions they refer to 3 degree rake. So i leveled the chassis front to back then lowered the front of the chassis down to a 2.5 degree angle/rake (that's as close to 3 as i can get), now this where I'm a bit lost. I am figuring i must level the new crossmember front to back while keeping the chassis still angled down 3 degrees/rake. Therefore the chassis will maintain the 3 degree angle/rake but the crossmember will be level with the road surface. 1 = can anyone verify if i am correct??? 2 = is 2.5 degrees/rake acceptable????

Moeman, why don't you post your question separately so that this topic doesn't become confusing?

Looking at CPP's website, for E4754M2IFS-K, it says:

Instructions:
1. Start with the truck or frame securely on jack stands with the frame set to the same rake angle as the truck will be when completed.
(Typically, the frame is at a 3-degree slope so the rear is slightly higher than the front.)
If the suspension is installed at the wrong rake angle, you may not be able to align the front end with the correct amount of caster.

Are you using jack stands? Use something solid underneath the jack stand base to make final height adjustments.

The screw-type leveling jacks used with a travel trailer make it pretty simple to set up a frame level, or at whatever rake angle you want. Installing some large anchor bolts in a concrete floor allows a chassis builder to anchor the frame down with ratcheting chain binders for a really solid base to work from. We used 1" diameter female thread sockets installed into a level floor when building or repairing race car frames. When the surface plate was not in use, just unbolting the chain anchor points made that bay useful for general maintenance work.
Jerry

thanks buoymaker, i am using jake stands, i also spoke with cpp and they verified what i was saying was correct.

I just had a Mustang II front end installed in my 46. My truck already had a V8 installed. Questions have come up about it’s safety. I feel it is safer than original. The front of my frame is boxed up to the cab. You have to box the frame to put the crossmember in the frame. I now have 11 inch disc on the front. The truck rides and drives a lot better. The original question was about clearance for the 6 cylinder motor. With all the folks out there selling Mustang II front ends I’m sure someone has addressed that question. The only thing that I found you have to ask is “ do you need a strut on the bottom control arm?” If you use original Mustang II control arms and some tubular control arms you have to have a strut or brace on the bottom control arm. The Mustang II should drop the front end 2 to 4 inches. You can stiffen up the front end for loads by changing the spring rate. I had 400 pound springs in mine and it was like a chuck wagon. I think I dropped down to 325 pound. The old 6 is 100 pounds heavier than the V8. Do your research first. Talk to these companies and they should answer you questions before you buy. Good luck.

Maybe you could look into different kinds of IFS swaps, which may (or not!) fit your engine better: Corvette IFS (Flat out engineering, among others) or the "traditional" mid-'70s Camaro front clip.