Unfortunately, you are even more limited with stock o.e. C5 Z06 wheels. Frankly, this is so because multiple Plus 0 tire sizing (i.e., 305/30-18 for the rear, AND, 275/35-17 matching Plus 0 fronts for the Corvette C5 Z06), and, such availability is sadly virtually non-existent for the C5 Z06 except in a rear drag radial tire (i.e., Hoosiers A3S05's, and, Kumho's ECSTA V700 in an competition only 305/30-18 tire with 6/32 T.D.). Moreover, a 10.5 inch wide wheel can accommodate an 295mm tire, AND, an 305mm tire, as well. However, actual appropriate tire sizing availability will always be the deciding factor. It is because of these issues that many C5 owners opt for purchasing true aftermarket custom wheels in 18, 19, and, even 20 inch diameter wheels. Custom wheels CAN be made into many different wheel widths, and, custom offset fitments to accommodate a wider range of tire sizing that is still dependent upon the specific application (vehicle type), and, performance goals of the consumer (daily driver, or, dedicated track car). Good luck to you.