Sorry, still thinking about your question. 15" wheels? do you self a favor and find the tires first before you make that decision, same is true for 16" wheels, 17" are a little easier, but many guys are moving to 18" for tire availability. If the wheels are built right you can run 9 & 11's, problem is these will probably have to be custom built to completely eliminate the spacers. Porsche 930 originally ran a spacer up front, then they built one into the actual front hub assembly. In the rear I would plan on a 1" spacer and even then I am basing that on the available outer rims available. When I built several of the very deep offsets, I used 2.75 or 2.25" outer lip on the front and it looks proportional correct with a 4.25 or 4.75" rear outer lip. 9 & 11, or 8.5 & 11.25/.5 just depends on which size hoops are used. Jim