Transplanting any 1973-later rear axle from a 1/2 ton truck will require a little bit of fabricating. The 1973-later trucks use leaf spring rear suspensions with no panhard bar. 1963-72 1/2 ton trucks use virtually the same axle set ups. So, these would be a slam dunk bolt in, other than the correct length panhard bar. 1965-72 used the same length panhard bar, 1963-64 used a longer panhard bar, and 1960-62 used a slightly longer panhard bar.
To transplant a 1973-later rear axle requires changing the axle tube spring pads, and aquiring a panahard bar relocating kit. Or, if you are really skilled with the plasma cutter and welder, which I am not, you can cut the panhard bar mounting brackets from the 1963-64 rear axle and weld it to your donor axle. This is not possible with 1965-72 rear axles, as the panhard bar mounting point is cast into the differential housing.
Good Luck!
