Will a 15" wheel fit on my 63 Dart

15" wheel will work fine with that tire. Problem will be finding a 15" wheel with small bolt pattern. They are available by vintage wheel and stockton wheel. However I don't think the factory made any 15" small bolt pattern wheels.

I don't know the factory backspacing as it depends on the wheel and width but it was probably close to 3.5" +/- a quarter inch