What size do I need?

I have a stock A-body 8 3/4 in my 68 Dart. I'm currently running some street tires and rims on it now (15x8 with 275's). I want to get a Strip set up but don't want to cut the housing down. I'd like to run 15x10 with a 325/50/15 tire. My car is mini tubbed and leafs re-located. What back spacing do I need to run this size set up?