18" will work with the right offset..........I have run my Topline 5 spoke Y2K chrome repos 18 x 10.5 +58mm offset wheels w/o issue on the back.
"thegreenman" has them now for his C6.........we test fit them in the driveway before he would buy them..........the nerve!
The fronts need to be a 18 x 9.5 with around +58mm for a big brake kit.
OR
Buy my HRE wheels & tires and I guarantee they will fit
