Dave,
I haven't changed a thing on my Cobra. It still has the original wheels and tires that came on it from the factory. So I can't tell you about back spacing or anything. You might try the 15" rims and if the back spacing is to much, they make spacers that you can get to help, but then you may have to change the studs for the lug nuts to longer ones. Sorry that I can't help you on that one.
Ron
