When it is nice hot and dry you might want to seal off the side that was not welded so that Water/Salt does not get inside and rust away the Weld.

JB Weld Epoxy would also add a tiny bit of strength and keep it from flexing from side to side. Fill the groove as best you can and use Masking Tape over the Epoxy to keep it from running out.
It will take about 4 hours to cure.

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84 300D, 82 Volvo 244Gl Diesel