And depending on the offset of the wheel it could be possible to actually still clear the Hicas.. As you aren't really worring about the tire touching Hicas but rather wheel itself. Since the wheel is a 315 a 18x11 would be ideal however an 18x10 would still be able fit the 315 tire..
I really don't know for sure GR but I have seen 315" and I think there is a possibility of it working just no one has bothered to try quite yet...