finding a 8.25 rear for an A Body

You would be best to just get an 8 3/4 rear buddy, several folks here have up for sale.

Parts are easy to get to.
8.75
http://www.forabodiesonly.com/mopar/showthread.php?t=82629

Here is an 8.25 too.
http://www.forabodiesonly.com/mopar/showthread.php?t=82527