I have aftermarket 03/04 Cobra wheels on my S197, see my Pics. They are 18 x 9 with a 26mm offset and 6.XX backspacing and they fit, however they stick out past the fenders but i like that look.
I have seen pictures of guys running Stock 03/04 17" Cobra wheels on their S197's, thats what gave me the idea of running the 99 - 04 offset in the first place, so it should fit. I have seen an S197 running the 10th anniversary Cobra wheels and it looks really sharp! unfortunately they dont make them in 18".
I found the Cobra wheels on ebay made by "AFS", 18" with Black painted cut outs, it looks just like the Cobra wheel but the closer you get the more you realize its a custom wheel, gets great reactions at the shows.
__________________ 2007 GT Convertible Premium 5 spd || FRPP HotRod Cams || Full Steeda Suspension w D-Specs || Brembo GT500 || Steeda CAI & Delete plates|| Flowmaster || Magnaflow catted X Pipe || MGW Shifter || Tuned by RealSpeed || |