I'm going to have to get under someone's '05 and see why my '01 can fit larger tires than they can, and that's with wells several inches smaller across.

I'm thinking the only thing in the way as the fatter tire travels up is the soft plastic skirt, not sheet metal...and we only need about 10 mm to get room inboard of a 285 to where a 305 would need to clear.

If there's sheet metal sticking out w/in that difference, it can probably be BFH'd to clear the contact point, etc.