Are all 8 3/4 axle shafts same diameter ?

what size brakes are on the 7 1/4 rear? if they are the 10" version save the drum & all the parts , the backing plate can be made to mount to the 8 3/4 by drilling an extra hole.
The other cars 8 3/4 has a different offset & size for the the brakes , you will need A body only parts for an a body 8 3/4 rear. Lawrence