tire to fender lip clearance

The fenderlip is not the issue.
It's the narrowing ridge on the inner wheelwell that causes rubbing usually. At least if you have your car at the normal or lower than stock ride height.

Since you'll be running a 45-series tire I will presume you like handling and your car's stance will be slightly lower than stock. But with the soft rubber bushings I would at least try to keep 1" between tire and inner wheelwell ridge.
Body roll will affect tire rubbing as well. With some good swaybars and shocks you might can get away with 3/4".