The Stovebolt Site Forums The Parking Lot '60-'66 Trucks 77' crew cab to 66' GMC/Chevy swap

First off – What a fantastic web site!!

I currently have a '77 GMC 3/4ton Crew Cab that I’ve owned for the past twenty-five years. I’ve painted it outside twice and replaced the doors fenders and hood but time has finally caught up with it. It spent it’s early years as a truck on a Texas Cattle Ranch and the winter salt has done it in.

I want to keep the 502 crate motor I put in it as well as the turbo trans. Both have very low mileage on them. The 502 is the high torque towing engine. I’ll also swap over the over load springs on the '77 to the '64-'66. I need another towing vehicle for my toybox trailer and I’m looking at the 1964-66 GMC/Chevy 3/4ton trucks. . I understand in 66 the 3/4ton GMCs went to leaf springs on the rear and Chevy stuck with the coils. I love the body style on these trucks and because of the year I won’t have to worry about the smog inspection here in the People’s Republic of California.

The toybox trailer (not a fifth wheel) is 21’ and loaded weighs about 7-8,000 lbs. I plan on swapping the brakes front and rear to power disc. and installing power steering. One of the things I don’t like on my '77 is the full floating rear axle which requires pulling the axles to do the drum brakes. I also didn’t have much luck looking for a disc conversion for the '77 rear end.

My Questions are:

1. Will my 502 and turbo trans fit in the 64-66 trucks?
2. Is there a problem pulling that much weight with the older 3/4ton trucks?
3. What rear end (not ring and pinion) would you recommend for this application that would be an easy fit? Concerning gearing of the rear end my '77 has 3.73 gears and I’d like something a little taller for lower RPMs at cruising speeds. Gearvendor over drives are a little pricy.
4. Would I have to stiffen up/reinforce the frame any. I understand that in 67 they went to thicker frame rails.
5. How about gas tanks? My '77 has saddle tanks with a total capacity of 40 gals. What gas tank options do I have for tanks that fit inside the frame rails that will give me a reasonable driving range?

Any assistance will be greatly appreciated! I’d like to be doing the conversion by early summer. That way I can start now with accumulating the parts needed and of course a '64-'66 truck.

Thanks again!
Gunnar
So. California

the engine and trans should fit fine. Have seen alot of big blocks and turbo trans in the trucks. The 3/4ton frame shouldn't have a problem pulling that kinda weight.

If you're planning to do towing, you'll want to keep that 3.73 gear. Also, you'll want to keep the full floater, as it's much stronger that the semi floaters. For disk brakes, check out the '01-'07 GM 3/4 ton trucks, the smallblock powered 3/4 tons used the same 14 bolt rearend with disk brakes, should be an easy swap.

hi guy .im doing a 66 gmc/chevy crew cab to a 86 chevy crew cab single wheel ,frame ,and was told the 66 truck will not fit the 73 and newer chassis -due to the kick ups front and rear? my 66 crewie chassis was a piece of junk when stretched and some previous owners really screwed it up !i have seen in c the "classis trucks " magazine a green and white 65 crew cab truck that was mounted on a 78 ? chassis ! it was located in the tucson ariz. area ? if i could find the owner to verify what was used it would be great ! any way let us know if you get body to chassis w/ some pics ?thanks mike "carryallman" wahl norwalk iowa

Thanks for the info but I want to make sure I understand you correctly. Are you saying that the disc brake assembly on the rear ends of '01-'07 will fit onto my '77 full floater that I can then put under the'66. Or did you mean that it would be easy to take the whole rear end assembly off an '01 -'07 (brakes, rear axle etc.)and put it under the '66. I'm hoping you meant the former! But that would be too easy and no fun, right?

Thanks again for the info!

I did mean that the brake assemblies would be an easy swap to the older axle. The '01-'07 axle is wider, without knowing what type of bed you're running, that could be an issue. If you're running a flatbed, I don't see a problem with running the entire axle assembly, as width isn't as much of an issue.

Howdy Gunns,

My '64 half ton coil spring truck regularly tows 10,000 pounds no problem. Fit an aftermarket tank under the bed behind the rear axle in addition to the behind the seat tank. Fitting the body to the frame is just a matter of building the mounts. Good luck and how 'bout some pics.

Longboxx55, do you know if the '01 to '07 brake assemblies will fit the original '66 3/4 ton?

here is an example of what the mounting looks like when someone puts a 64-66 on ab 84 4 x 4 frame. I bought it that way but just for the suburban body that was on it. it would never pass inspection here. and you have to alter frame length.
mind you would could build better mounting for the application, but gives you an idea of the difference.
I do believe that the suburban frames has a lesser rise in the 73-91 years than the pickups
http://www.chevytalk.org/fusionbb/showtopic.php?tid/275398/
ron