Don't forget that certain tire manufacturer's tires are slightly wider than others. For example when I ran Continental tires and then switched to Nitto's the Nitto's were slightly wider.
If anything you should be fine. Maybe a slight amount of rub if you turn the steering wheel full left or right, but again that depends on the tire manufacturer.
If you are running the saleen wheels you should go with what they recommend. They run a 265-35-18 on the front and a 295-35-18 on the rear.
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