I had to relieve the center bore on the Nissan Frontier wheels I got for rally, but I used a die-grinder for that and just removed a little material. It depends a great deal on the wheel though. Your best bet is to take them to your local machine shop and let them advise you and also perform the work. This is a very simple procedure for any basic machine shop and should cost you less than $100 for all four wheels. Even though only the front wheels require it, you'll still want to be able to rotate your wheels if needed.