i ran 325/50's on my 66 belvedere but we had to work to get em in there, we swelled the body out 1.5", cut the front edge of the body forward the inner fender edge to and i moved the springs in 1.5" or so and built a dana 60 that was wider, i ran a 4.5" backspaced 8" wheel. it looked great but that was all of the tire that you could get under it, next to a friends stock 66 you couldent tell the differance in the swelled rear wheelwells