You can make those work. The backing plates don't care what size bolt pattern the axles are. Moser makes LBP axles for use with the A-Body 1.75" brakes. You would probably have to redrill drums, but that's easy.
A30-CST-A45 - A-Body, 8 3/4" Rear Axle Shafts, Stock A-Body Drum Brake (Redrilled) -- 30 (Pair) - Moser Engineering
The beauty of it is you have a blank sheet of paper and can put together whatever you need.
If you need a back braced housing, maybe consider something stronger than an 8.75, like a Dana. If you already have the 8.75 pig set up though, that's different.
