i have a 58' that is on a 67'-72' frame and it seems to fit just fine. at the present time mine is 8-lug but i have all of the parts from a 75' 1/2 ton to change it to a 5-lug setup with disc brakes. the only thing i could see that were really custom was the rear cab mounts, they had 4" spacers but the rest of the swap looked pretty normal to me.
