Tire Clearance

I have almost the same setup, 215x65 on a 15x6 rim with 3.75 backspace on the Valiant. It only has a very minor rub at full lock to the right when moving at speed. My suspension is still the original 54 year old stuff, so I suspect when it's rebuilt the rubbing will go away. Your Dart and my Valiant should be the same so I think you will be OK.