So the wheel wells are galvanized steel - got it. I waited to replace them until I got my new axle on. By doing this, I could not slide the "lips" under the floor. So I bent some new galvanized and slid it under the plywood floor and then rivoted it to the original wheel wells. Sanded the rust off, primed them, and then used the underbody coating. Lots of Tempro 636 in the corners to prevent water from getting in. Hope it works.