Wheel suggestions

Your best bet is to measure what you have now as a starting point, install them on the car and look in what direction you have room to move wider in and figure out what will fit your car. Then decide do I live with what's available in SBP or spend the money on a LBP conversion and then decide if you want to compromise size for a staggered wheel and tire combo or run the same all around.

Also consider the use of the car. Do you plan to drive it hard and/or at modern freeway speeds? Are you drag or autocross racing the car? how close to original or stock looking do you want it to remain?

Your going to hear people say they fit all kids of tires and the bottom line is not all A-bodys are the same for tire fitment. What may fit a Barracuda or Duster in will not fit your Dart. On tires, come to understand their ratings (if you don't all ready) and see what you get in 15" vs 17". Tires are part of braking (and handling) capacity too, so back to how you intend to drive the car.