what size SBP wheels can we fit under a rear 1963 fender?

Those are stock 14x5.5's
what size on the rear?? any rear modifiations on that car?? think i might get the 15x7 and raise the car a little bit if i need to... i have coil overs on the rear so i think it might be alittler higher in rear then stock not exactly sure... gonna talk to a friend that has a wheel shop and see if he has anything same size to test fit.