Stock is
18x9.5 275/35/18
19x12 325/30/19.
If I buy aftermarket - I'd probably stick to similar sizes or do 19/20. 20 is too big up front I think.
Surprisingly the contact patch with 345s is pretty much the same as the 325 due to differences in the sidewall etc (someone measured them on corvetteforum).
However the Traction Control/Active Handling really gets messed up when you change tire sizes even a little bit and strange error messages come up when doing 120+.