It doesn't really matter if you have 15" wheels or 22" wheels, 255 in front and 275 in back is about all you can do for a car this low, without a lot of inner fender surgery, and even then, the offset has to be just right +/-.25" for these sizes to work without rubbing (and the perfect offset is different from the front and rear, so even the same width F/R wheels would need different offsets to be perfect)
Pounding, cutting, beating and rolling with make a little larger tire fit, but 255F/275R is the practical limit before surgery is required.
