I installed 73 up discs on my 67 Dart when I had it. I had either 215 70 14 or 225 70 14 on a rallye wheel which is 4.25 bs I believe before the switch. I mounted same tires on bbp rallye wheels with same backspace. I had to go from a 70 series tire on the front to a shorter 60 series because of the tires rubbing the front of the fenders. The switch to the discs definitely moved the wheels out a noticeable difference.