I use a Makita grinder (4 inch) with the thin grinding disk, mark my cuts carefully, and dive in. I butt weld everything using butt weld clamps and very careful welding to not warp the metal. If done carefully, you cant tell the panel was ever replaced. I use a wire feed mig and a lot of patience. Ive replaced everything available for these trucks at one time or another, and the steps are always the same.