for garage bodywork a cheap mig welder would work great. You don't need much power since the heaviest body work would be would be MAYBE 16 gauge probably more like 18. I'm doing up an old 68 250S (check the website in my signature). I used a mig welder and after: grinding with a DA sander, sanding with a scotch brite, then hammer and dolly work only a SMALL amount of filler would be necessary. By small I mean about 1/16 inch deep. This is the best bet if your a DIYer. I have used TIG quite a bit for work but it's a LOT harder to learn and you have to have perfect fit pieces and weld on a regular basis.

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'78 300D 85,000 original miles drive her daily