I would like to know if anybody has an idea of what size (largest) tire I could put on the rear of my 67 Belvedere. The car has P235/70R15 on 8 inch rims (with 41/2 inch backspacing). I would like to put a pair of 255/60R15 tires on the rear. The rear fenderwells have not been modified. Any help would be truly appreciated.......Thanks