A body 8 3/4 housing width

Marcohotrod said
and axle flange to axle flange is 57"

This is not correct! Drum face to Drum face is about 57"

Here is an original A-body rear I sold with measurements listed in the description

http://www.forabodiesonly.com/mopar/showthread.php?t=298735&highlight=8-3/4+3.91