Confused about tires

I've looked with the search feature and only got more confused. Please help. I have a stock Duster (1974), automatic, slant six, with a 7.25 inch rear end. It currently has 14 inch stock wheels on it. I want to get bigger tires and Cragar SS supersport mags. With my configuration, what is the largest size of tire and wheel that I can fit without any rubbing? I like the look of the wheels/tires being partially covered by the wheel well. I don't want to modify the wheel well.