1980s Cab and Front Sheet Metal on 1970s Frame

[Kilian]

What are the known issues to be aware of when transferring a cab and front end sheet metal from an 81-87 truck onto a 1970s frame? Are there some previous threads on this site that have the details?

I see in the parts catalogs that there are different cab mounts for the 80 and older trucks compared to the 81-87s. Just wondering if it's a difference in the frame, the cab mounts, etc. Same with the front bumpers and radiator supports.

I found a pristine (at least for Wisconsin) 3/4 ton 4x4 frame for my project of transferring the front end/cab/bed of my 1983 GMC C2500 and get a 4x4. However, the frame is 1976 or older, based on the front frame tips, Dana 44 flat top knuckles, full-time transfer case, and 1st series locked hubs.

Thought of this after the initial post...truck and frame are regular cab, long box.

 

[AKguy]

I am putting 1981 C20 (454/TH400) metal/engine on a 1980 K30 (350/TH400) frame. I am using energy suspension rubber mounts and my own fabricated plates/bushings. The cab mounting locations are the same but the heights differ. I had to move the core support mounting holes rearward about an inch or so and had to relocate the motor mount holes, although not far, far enough I welded the old ones up and drilled new. Of course, I cut the hump out of the K30 and used that. Yes, The front frame horns are different but I have not tackled the bumper mounting yet, don’t see that as being difficult. The support arm from the NP205 to the bellhousing needed a few washers to make up the gap. Shifter linkage, no change. The exhaust downpipes had to be lengthened. Not sure I would ever do this type of project again due to the time and issues with different parts involved. However, I will have what I want in the end which I can’t get with the newer trucks.