72 Demon rear tires

I have 295-50s on the rear of my Duster. 8-1/4 rear bbp. Wheels are 15x8 with 3.75 backspace. With Super Stock springs they don't hit or rub the quarter panel, but with the old worn out /6 springs they would rub if I hit a big bump in the road. There is about 1/2- 3/4" clearance from the tire to the springs.