Several guys here in h-town are running the C5 Z06 rear wheels in 18 x 10.5 with a 53mm offset. This offset fits perfect on the rear with a 305/45/18 or a 305/35/18 and no spacer required. You do however need to zip-tie the e-brake cables back a bit.
There's at least 9 or 10 Camaros here with that set-up and mine is coming in this week sometime
Hope this helps
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