Rear wheel and tire combo ???

PA Dodger said
I had 15x7s with 4 1/4" BS and 255/60-15s on my '69 Dart.

Exactly the same here. 225/60-15. I tried 235/60-15 and they would rub somewhere all the time. So I think if you want to modify nothing, the 225 is the right size tire.