The bolt pattern is 4 1/4. I bought some high quality wheel adapters to get it to 4 1/2. Since this will be a street driven car, I am not worried about using adapters. I widened the rear fenders 2" each and moved the rear running board brackets out as well. The side splash aprons are still even with the rear quarters. You can't tell it was altered unless you know what you are looking for.