Dang it, I hate getting old!
One of the mods for the MIII is to widen the wheel well to fit the 315's.
But, that is mostly a cosmetic change. People who race don't like the 315's. They're so wide on such a light weight car that it's tough to get some heat in to them, and they don't stick. But they sure look great. And, on the street, I don't think it will matter.