Alternator Troubles! 1973 Plymouth duster 318

Old alternator may be worth fixing. The squarebacks are pretty easy to replace most of the parts on as needed.
A lot of new alternators have high draw rotors that result in short life for the votlage regulators. :(

Regardless. Put that battery on a charger.
Recharging a battery thats really low with the alternator is a good way to damage stuff (connectors, battery itself, sometimes the ammeter)

The ammeter needle should never be more than 1/2 way either direction for any length of time. That's about 20 amps. You can get away with that for a few minutes but not much more. Full scale each way is about 40 amps and that is danger for sure. Shut it down if it goes there.