What Wheel Backspacing for an F-Body 8.25 in an A-Body?

Does anyone have good places to get used wheels? My local Picknpull doesn't sell just wheels, they only sell full wheel/tire sets (all 4) and I only need two wheels, and don't really want any tires. Planning on checking out a few other local yards to see what they've got, but I expected the bbp wheels to be easier to find. Lengths on that axle will be coming as soon as I can convince a family member to help me hold a tape and straightedge in the rain.