looking for good info for swaps

Use an 8 3/4 rearend out of a 65-67 B-body. It's already big bolt pattern to match your disc brake set-up(assuming you will be using the single piston caliper set-up off of a 73-76 A-body), it'll drop right in and is much easier to find than the elusive A-body housing, you,ll have to change the left handed studs in the driver side axle to right handed(easy as pie though).