There is an off the shelf 18X10.5 (Enkei RPF1 I think) that works fine. Might need a spacer or something, I don't remember. If you go custom wheel I'm sure you could go 11" and probably more no sweat, probably without cutting. Keep an eye on your spindles.
Oh, forgot to add. We ran 315/whatever-18s on the 2005 I drove a couple years ago on those RPF1s.