[66-PMD-GMC]

Originally Posted by SCOTI

You might consider adding spacers for the rear cab mounts & getting longer rear bolts. I built new ones (from the old ones) only because I added gusset/fish plates to my rails which changed the width dimensions. Since the mounts were going to be off, I just re-did them w/the right dimensions. A stock width frame could utilize some 1" spacers under the cab bushings & would be good to go. Rattle can them black & use a poker face. I won't tell

I measured the frame width on both frames and they are identical within a 1/16 of and inch. The datum holes are also in the same place, dead on, on both frames. (holes used for taking measurements during build and repair of vehicles)
Using these holes as the guide, I find that only the rear cab mounts and front cross members/supports under the radiator are in question.
Are you saying you are finding the front cab mounts in a different location between the 2 year groups? (63-66 and 67-72)
Also, I find that the GMC and Chevy radiator supports are different throughout 60-66 making this quite a mixed bag. So this all will depend on what my desired end result is. Yes?
Theoretically I should be able to strip the brackets and bracing from the 66 frame and use it all on the 69 frame and other than the frame horns, it would be a bolt together deal.
I am generating a blue print as I go since I have been unable to find any prints on the 63-66 GMC frames, only Chevy.
I do have 67-69 prints for what they are but my rudimentary initial measurements tell me there is more similar than dissimilar between the year groups of frames here.