The Corvette has 17x8.5s (245/45ZR17) on the front and 18x9.5s (275/40ZR18) on the rear.
You could probably just stick with 17x9s all around and go with 245/45ZR17 on front and 275/40ZR17 on the rear.
Those would be good sizes.
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351W 89 Mustang GT Convertible