wheel and tire size

I have 215/60-15 tires on 6.5 rally with stock 4.25 backspace that work well on a 69 Dart with 73 up front disc setup and an 8.25 rear to get BBP all around.

You may need to get smaller diameter tires.

Using one of these online calculators...you can find out what you need, like this one: http://tire-size-conversion.com/tire-size-calculator/. Google tire size calculator...you might find a nicer one.