you would be welding to the wheel well right? they are pretty thin, 20 or 22 gauge. and only 1 layer. A weld would not do,
IF you are going to do this, you should think about bolting in a larger plate to the underside and maybe even the top side of the wheel well, sandwiching things together.. that way it will never pull through.
or do what bonzo said, similar idea
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