Yes, 4.5 backspacing on front. Tires are 235.40.18, front end lowered 3" inches. No tire rubbing, as you know on 69 GTO's with the back of the front wheels, they will or can rub on the fenders.
Actually lowering the car helps eliminate that problem.
P.S. That's not dirt on the fender. That is the reflection of the pavement.
R.P.