[WSSix]

I believe you can get a 305 if you roll the fender lip and remove the rear seat belt bulge that's at the front of the well. How low you go with the ride height will have a huge effect on this, too. The fenders are draped/streched over the wheels. You can't go up into the well much at all before you're hitting the top of the well.

You can definitely fit a 305 or 315 if you do a DIY mini tub by cutting out the inner fender and moving it over just enough so that the inner part is flush with the the frame rail. Before DSE came along, this is how it was done. It's like a 2 or 3 inch widening. The design of the tubs is such that you end up welding in a flat sheet of metal, not a fancy contoured piece. Get under the car and look up into the wheel well and you should notice the frame rail sits to the inside of the tub and the top of the tubs where they are welded together is fairly uniform and flat. You're just moving the tub over enough to take advantage of the space that's available without cutting into the rail.

Good luck. Spend some time trying to get the widest tire up front that you can, too.