B-Body Axle?

I have a 69 Barracuda with a 7 1/4" differential and am eager to upgrade, to 8 3/4" if possible but also am considering 8 1/4".

Are all A-body rear axles the same dimension (52 5/8" flange to flange)?

I'm going to upgrade to 74 Dart front disk brakes, which I've heard will bring my wheels out about 1" on each side...so would using an E-body axle be fine when I have to change to new wheels, and that would allow me to get the same offset wheels front and back (as mentioned in this thread)? BTW, can I use 14" big bolt pattern wheels with 11.75" rotors? Or will I need 15" wheels?