So I bought an 8.75" B body housing, axles and perches for $200...

Depending on the year B body it came out of, you may not really need to narrow it at all. Just move the perches and use a little more backspace on your wheels.
As far as the drums go-
10” Drum Brakes Options for A-Body 8-3/4 with Moser Engineering BBP Axles