I'd use a cut-off tool to cut out the damage, same gauge steel at least 2" longer than the total length of your damaged area, and a bead roller to re-shape the bead. Shape it with your hammers & dollys after running your bead to fit the body. Weld by spots no closer than 1" around edges, grinding welds after you get some on all sides. Weld using this pattern until you have welded & ground to solid. Remember that the grinder creates heat also- so go slow and allow the metal to cool between spots.