Turns out the battery hold-down had been replaced with a threaded rod with the wrong thread pitch, so I had to unjam it & chase the threads. The tray was also bent, and both battery terminals had to be cleaned & straightened. The positive nut was rounded. I soldered a new 8ga GXL black wire to the hacked harness grounds, and crimped new rings on. It's long enough to connect more-originally, next time the battery terminals need replacing. But I polished the unusual lead terminal in the negative cable so it's well-grounded now.
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Owner caption March 2020 · Photo 123 of 157