The compatibility problems with different boxes largely boils down to output shaft, or sector shaft size. First, there are two sector sizes, simply known as large or small sector. The large sector, just above the splines as it exits the housing, measures 1.22". The small sector measures 1.11".

62-76 A-bodies, 62-72 B-bodies, and 70-74 E-bodies all used the same manual box. Most of these boxes used bushings throughout, however, the B-body V-8 units were built for more abuse and used bearings internally instead of the bushings.
All manual boxes used a small sector shaft with the exception of C-bodies and vans to 1988. The big cars and vans used a large sector, presumably for added strength. It's also assumed these boxes used bearings instead of bushings.