so just wondering

Good luck finding an A-body 8.75" rear, as they were rare even then.
C-bodies had 8.75", but much too wide so would need to cut both axle tubes and shorten both axles.
The reason many use the Ford 8.8" is they are common and cheap (Explorer), requires shortening only 1 axle tube and then using 2 "short side" axles, and a quick way to get rear disk brakes. Read the posts w/ many photos.