Here are the parts I have, what's the best approach?

I'm doing the same thing in a 66 Valiant. It's a slant with 4-speed OD, 8-3/4 with 3.55 gears and 10" rear drums. I kept the SBP front and rear, it wasn't hard at all to find parts. As mentioned above, most folks want to get rid of their SBP stuff to go BBP. That makes for some cheap shopping on behalf of those wanting SBP parts!