Dash power running through Alternator gauge?

briwill70 said

Definitely is not a fleet wiring situation. 2 door, 270 grandma car. Amp gauge wires are newish and upon closer inspection there appears to be some melted wires under the dash close to the firewall bulk connector. (probably the reason for the fix.) Everything was working before I disconnected so I'm inclined to just reconnect for now.

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Get a s'65 Dodge or Plymouth shop manual if you don't already have.
In the back of the electrical section there is a complete wiring diagram.
Use that to identify which wires show damage by color, size and position in the connector.
Then you'll have an idea of what to keep an eye out for problemwise.
Main headlight circuit is a common one.
Ignition circuit is also the alternator's control - and if that's damaged can mess up the voltage regulation.
The ammeter will only indirectly indicate voltage regulation problem. If it is charging high or showing charge for long periods, or following the engine speed - then look into this possibility,