Did you get a spark or smoke from somewhere when you grounded it? My experience with fusible link failure was a while back, as I recall I found it by wiggling wires, and one had a limp spot in it where the wire burned away in the sheath. That was on a Dodge Reliant where the battery was installed backwards (not by me).
You could do the voltmeter, or find a 24v buzzer like for the seat belt warning. That way, you can tie one end to the battery post (+ or - as appropriate) and not have to look around as you're touching terminals of the other polarity to check for voltage. Of course, tape things up so you don't create another short! Even a #18 wire gets painfully hot with 24v x 750 CCA.
I'd recommend a quick check of not only the positive side but also the ground side, there might be fewer connections on the ground side but if one got fried it would make a messy troubleshooting run.
Make sure to replace fusible links with fusible links or an inline fuse of the right size. Don't be tempted to replace with a standard wire - could create a fire hazard.
Good luck and I hope you find the fault quickly.
