The Stovebolt Site Forums The Shop Area General Truck Talk 51 GMC Body on 48 Chevy chassis ????

I have a 51 GMC long bed. I was going to chop the chassis to make it a short bed. the guy who was going to do it was charging me $700 for cutting the chassis and the bed. I just found a 48 chevy truck short bed chassis and was wondering if it is the exact same set (bolt ons) the only difference i saw was the brake lines and shock absorbers. im planning on going discs all around. the guy wants $150. one of dislikes of chopping the lond bed chassis is that i would lose the braces of the chassis around the back of the cab where the e brake is set up/ what do you guys think. my thinking is that it would be cheaper and in the long run safer because the chassis is in tact. the rest of the truck should bolt right in right?

I believe the cab is a direct bolt on, as they are identical between GMC and Chevy.
I suspect the radiator support will bolt to the frame the same because the fenders bolt to it, and the fenders although different by a light hole will interchange. That leaves the bed, and I bet it is the same or close enough to make it work with out much trouble.

I recommend you get the new frame, and not cut the other one.

Grigg

it should bolt on the cabs are pretty much the same but i believe the mounted a little different in 47/48 than the 49/50/51/52/53's, but i know for a fact the 49-53 are all the same. i have always been told that cutting your frame is real bad, no matter if a professional does it

I think you just saved $700 in cutting costs, but there will be moments that you might think different That's the charm of these nice trucks
Good luck

Its not that simple. The radiator on the GMC is further forward because of the longer motor. If you look at the front crossmember the Chevy and GMC are quite a bit different.

I do not think the radiator support from a GMC will simply bolt to the Chevy frame in the proper location.

Not to say it can't be done, but understand going in that either you will be swapping the front crossmember, or doing some other adapting to make it work.

This photo is a Chevy front crossmember with part of the motor mount still in place.

Chevy Crossmember

And this is a GMC front crossmember. Note how the radiator mount postion is lower and pushed further forward.

GMC Crossmember

The front crossmember is probably the most significant difference between a Chevy and GMC frame. Most anything changes more year to year than Chevy to GMC.

The rear mount difference is going to impact you a little differently. The hasp type rear mount of the later years should be easy to adapt since it simply bolts to the frame. The challenge will be getting the bolt holes in exactly the right place and with care that should not be a big deal. I'm not sure if the 3/4-ton rear mount is different than the 1/2-ton, that's where the rear mount may present more trouble.

I forgot to mention that i will be not be going with an inline 6. i am going with a 350 V8. I have an aftermarket crossmember for the V8 but will i still have a problem with the radiator support? I think i have to remove the stock crossmember (correct) Thanks guys i do appreciate you taking time to respond to my cries I just dont know if im doing the right thing by going with a different chassis, i just thought it would be better than chopping the other one. i have a 350 SB and a TH 400 tranny. i have both crossmembers and want to know what i need to watch our for.

Leave it alone. Long boxes are cool. :hammering:

, but to each his own

The radiator support also serves as the front mount for the fenders and grill. Without it all that front end sheet metal is just hanging off the front of the cab.

That crossmember is there for three reasons. 1) It stiffens the frame at the front spring perch. You don't want to loose that if you keep the original suspension. 2) It provides the front motor mount for the original motor. Not important if you are side mounting a motor. And 3) it mounts the radiator and front sheet metal.

Unless you are installing a Mustang II or similar IFS with a crossmember AND planning to fabricate new radiator and fender supports, you'll want to keep that crossmember.

ive been told by A LOT of people to leave it as original (long box) But my main reason that i want it short besides looks is that want to be able to fit in my garage. lol

OldSub I just might bribe you to come spend the summer out here in el paso tx with me to walk me through this LOL!!!! I dont want to touch the Short chassis at all so as far as the crossmembers do i have to remove it to get the V8 crossmember in or can i leave it alone and still bolt in the V8 crossmemeber this week end im comparing the two chassis then ill start bolting the front end in to see what i encounter. i hope it all goes well.

OldSub is right, the cross member/radiator support is crucial to a strong front-end. If you are gong planning on using the original GMC sheet-metal, the Chevrolet cross-member is located in the right place for the radiator support. I can't remember if I had to re-drill this piece to mount my radiator support after I changed out the GMC support for a Chevy. I do remember that everything fit afterwards.

Just want to confirm I understand you correctly. You can put the GMC radiator mount and thus the sheet-metal on the Chevy crossmember?

I've never done this, but have a Chevy frame I'd like to make a GMC out of...

OldSub, many years ago I installed a 235 in my 53 GMC Suburban. The original cross member was too far away from the the front engine mount. I replaced the cross member with one that I removed from a chevy truck and everything fit properly. I do not remember making any modifications and I no longer have that Suburban to check. I ground off the original rivets from the cross member and installed the chevy cross-member with bolts. I bolted my GMC sheet-metal and radiator to the cross-member.

Quote

Originally posted by OldSub:

I've never done this, but have a Chevy frame I'd like to make a GMC out of...

OldSub, look at the two cross-members and you will see the differences. They bolt up in the same place on the frame and they are similar excepting the GMC cross-member is shorter to except the longer 228 engine. No one told me that I could or couldn't do this swap, I just did it expecting it to work and it did...I was very young!

I swapped one from an Oakland built '54 GMC to a St. Louis built '54 GMC and had to to some rotary file work to get some of the bolts to line up.

Oldsub is right on with his knowledge. I was at a local restorer and rodder of these trucks this weekend. As always he has about five in various states of disasembly. He was commenting on one of his current builds is going to be a GMC with a V8. He says this works better than the Chevy because he says the radiator support sits lower and he can use a stock fan with a V8. I do believe that I have also heard him say that he has "made" a GMC frame from a Chevy as GMONIZ said.

This has been an interesting discussion.

In an earlier post I linked a couple of crossmember photos. Those two frames are currently sitting in my shop instead of out in the weeds. I may take some more pictures and get some measurements just to clarify some of this for myself...

any pictures or measurements OldSub?