Circle Racing Wheels is making an 17-20" version of the stock wheels. It's their 108 series. Has the four slots and nubs for C10 caps, 10 1/8". They're around $2200 for 18's. I'm going to use 14.5" CTS-V brakes and they said that it would be close but they'd probably fit since it's a spun rim instead of cast.
http://www.circleracing.com/108oe.htm
