Check around for somewhere where the big wires could touch something metal. Is you battery secure and tight? That big fuse blowing without blowing the others first tells me to start looking at the battery cable and starter relay/wires.

 

^ that. Has to be before the fuse box.

 

Well that's good to hear that it's back up and alive. But the guys are right. To blow the 30A fuse means something shorted between it and the fuse block. If you look at the wiring diagram, that doesn't leave many wires.

In fact, of the 4 wires coming out of that connector, the Red one is the one you need to follow. That wire provides power to the Fuse Block, the Ignition Switch, and the Regulator/Rectifier. The flickering tach is an indication of momentary loss's of power. That certainly indicates a short.

Good luck and let us know what you find.