Wheels for a '66 Dart GT?

15"x7" with 4.25" backspacing work great on all these cars. You can usually run 225/60-15 tires all around with no rubbing issues anywhere. My suggestion anyways.

If you really want to stick with 14" I'd still use a 7" with a 4.25" backspacing, only you'll want 215/70-14 tires.

Be aware that your selection of 15" tires is getting slim. 14" are even worse. Obviously, they are still out there though.