Fusible link guage?

One thing you can do to troubleshoot those kinds of problems without causing more smoke is to put a BIG test lamp in series with the battery ground.

It depends on the problem I'm trying to find.

If I have a low current battery drain, I want a small test lamp, so the normal commercial probe n lamp is fine

Certain other problems, I have a scrap tail/ stop socket, and so I can wire EITHER the stop or tail filament in, OR twist the wires on the socket together and wire BOTH stop and tail filaments into the circuit. The tail draws the least, the stop more, and the two of course together draw the most.

But for something you MAY have, that is, a massive short that blew up the link, I'd use something REALLY big, like a headlight bulb

First thing I'd check is the ALTERNATOR. If you blew up a diode, or somehow the charge wire got twisted over against ground, or if the insulator for the output stud broke, SHORT