Stock Tub and Rear Tire Clearance

My son's Dart is running 16x8 Torq Thrust 2's with 4.88 backspacing and 245-50-16s. They rub only when the chassis rolls over to one side, like turning into an inclined driveway (not too many of those here in Fla....).

4.5 b/s would probably rub the outer lip unless the car is raised up.....