8 3/4 vs Dana 60

There are a lot of guys here that would know better then me, but...the older Dana's in trucks weren't Dana 60's but where Dana 70's. As I remember the axle/axle bearings are different. Also, the overall length, obviously, is going to need be shortened to fit an A-body. It won't hurt my felings if I get corrected on this. No matter what you do, it's going to cost big $$$'s.
Mac