15X8 Cragar backspace ??

Depends on your tire size.

With an A-body 8 3/4 that has BBP axles and brakes, and the stock spring locations, you typically want a 15x8 that has about 4.5" of backspace to max out your tire size. With a 4.25” backspace you’re losing a 1/4" to the quarter.

So, you probably won’t be able to run a 275/60/15 without getting into the quarter lip, unless your cars ride height is pretty high in the back. But a 255/60/15 would probably still work. Just depends on what tires you want to run.