The magnum 500's do look nice.If I were doing 15 it would be 8" rear with 275/60 and 7" front with either 225/70 or 235/70.Why not consider the 17x8 all the way around?I was going to do that on my 70 Polara with 255/50 all the way around.But I sold the car after 19 years a month ago.