I have a 70 Challenger RT with what I believe to be the original 14" rallye wheels and P215/70R X 14 tires. Going to be upgrading to 15" rallye wheels and tires. The car is not driven hard or raced. What width rallye wheels should I buy and what size 15 " tires? Second question, my 14" wheel centers are excellent. Are they by any chance interchangeable with the 15" wheels? Thanks.