american racing Ansen Sprint Rims??????

Centerline autodrags that were drilled for 5x4 had a smaller center bore than the standard wheel to make sure they had enough meat for the small bolt pattern. As a result they used a smaller center cap that is real hard to find today.
I wonder if there is any way to find out what the center bore of that wheel is?

And, i'm not so sure that a 15x8 with a 4.25 backspace will work on the front. @72bluNblu ?