Biggest tire on Stock 67-69 Dart

Are you keeping the stock drum to drum width when you LBP or are you swapping to wider, more common brakes? This will change the rear off set to be more positive. My stock a body 8-3/4 housing with 11x2.5 rear brakes requires a 5.375 backspace on a 15x8 rim to be centered in the wheel well. If you swap to LBP fron discs, you need a more positive offset as well, like a 15x7 with a 4.5 bs, but can get away with less if you use a smaller tire like a 215 or 205.