Its possible, from the little bit of research I have done. seems your front cab mounts might almost line up, but the rear cab mounts, as well as the bed mounts will need to be fabricated. also the rear axle section on the 73-87 frame has a big curve, where the earlier trucks are straight. So either needs body lift, or fabrication to frame or bed, to make it work.
Thanks What I have is a cab and Front clip from c50 .the chassis is 84 3/4 ton 4x4 . So flat bed would look good
