I would be glad to help. Just need you to post the offset on these rims you are looking at right now.
Just some FYI, typically the late C4 models won't accept a later 11" rear rim withough sticking out the fender a tad. A 11" will fit - but not on the standard ZR1 offset - or C5. I am not yet sure about the 06 Z06 - and since these are not stock diameter - I am curious what they came off of and what the offset is.