Rear brake question

You can have the axle machined for the OEM early A-body bearing location and small drum register and keep the brake assemblies you have, but redrill the drums for the bigger bolt pattern

If the axle is machined for the E & B body bearing locations and large drum register, you will have to use the E & B body brake assemblies.

The bearing location and register size goes along with the brakes used because of the brake size & offset. You need to provide that info when ordering the axles.