67 Dart- Can I fit 15x7 wheels both front/back?

7" wheel with 4.50 backspacing will work front or rear. But no guarantees that anything bigger than a 225/60-15 tire will fit.
8" wheel with about 5" backspacing will work in the rear, but you are still limited by tire size. Some people can get a 235 tire on the back, some even bigger.