I've got 245/60R15 tires, on 15" X 7" wheels, with 4 1/4" backspacing on my '71 Dart GT. It has the factory installed 8 3/4" rear end. It also has ManciniRacing 2800lb springs, courtesy of the previous owner, in the stock location(s). The next time I need tires, I'll go with 255/60R15 tires.