Shouldn't be any problem - depending on the offset. Plus you'll gain about 1/8" more clearance on the strut side compared to my 18's because the strut slopes inward as it goes up.
For the street I'm running 265/40-18's on 18x9.5"x +45 offset wheels. Before that I was running 255/45-18's (same wheel and tire size as our years of the GT500). No rub or sticking out past the sheetmetal with either tires.
And out back, although it's close even my track day set of 285/35-18's on 18x11's don't stick out past the flare (looking straight down). I did remove the rear shipping tie-down points above the bump stop pads, though. The front wheels/tires in this picture are the same as the rears but with a different offset that just barely clears the struts and these do stick out a bit (although the tire tread is fully under the flare looking down here, too).