'71 340 Duster has a short

Fuse box looked ok...found the firewall connector to be melted where the main power wire goes through. Pulled out the bad wires and plan to push through new wires tomorrow. Also plan to rewire the alternator over to the starter relay with a fusable link. Black wire coming into the cabin was melted...certainly got very hot at some point. The amp gauge has been converted to a voltmeter and the red and black wires are crimped together behind the dash.

Will there be continuity on the cabin side due to the voltmeter and/or dome light bulb? We still have continuity to ground when checking the larger red wire in the cabin before it passes through the firewall ...not sure if thats normal or indicates a problem??

I can look up and see the connections and everything looks ok externally. Our plan is to temp wire everything and see if it still blows the fusible link...if so, we'll keep digging looking at the voltmeter and dome light...if not, we'll fire it up and then solder /shrink wrap it up. Thanks a bunch for the advice...I feel like I'm getting closer!