Ray,
I used an adapter to my arc welder called a "stitch welder" to repair my hacked up 66 Hardtop radio slot. It replicates spot welds. My first attempt never got used, the replacement patch. It was too thin. I made sections of the ends with the inward bends like the original dash and with a few backing pieces of sheet metal, some grinding, spot putty, made it work. I also used a couple of welding pads to protect the interior. A friend had his done in a shop but the under dash harness was out and that made it easier.
Jim