You also need to verify that you have E body brake assemblies. They have a little more offset then A body drums. Your axles need to match the brake assemblies and that will ultimately determine overall axle width.
I believe all 8 3/4 A body rear ends have the small 4" BC.
the B and E body 8 3/4 rears I've work on axles extend further from the tube end, but they also had wider brake drums.
they also have the larger 4 1/2" BC.
I installed a B body, narrowed 8 3/4 rear end in my 65. Updated the front end to 74 A body discs to get the larger 4 1/2 BC.
