Are you lowered? If you are you might need to roll fenders at an extreme case.
It seems that every car is different when it comes to large width wheels you may have to take a hammer to your inner fenders to make clearance. But before you do anything, mount the wheels. Put a pair of jackstands under the rear because you might end up taking the wheels on and off for test fitting.
Theres tons of write ups on LS1tech about the "BFH" mod. I'm running 17x11's with a 315 on some decent lowering springs and I only encounter problems when I hit big bumps. My next combo is 18x10.5 with a 315 rear tire and just the wheels without the tires they didn't have any clearance issues.
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