65 Ammeter now shows overcharge when accelerated

Here's the deal. "Running" battery voltage with the battery charged up, (and a good battery, meaning "nothing wrong" with it) should run no less than 13.5, no more than 14.5, and optimum is 13.8......14.2. This is measured AT the battery, warm.

As you add loads, like stereo, headlights, blower, AC, etc, that voltage will try and sag a bit as the alternator gets "topped out" trying to keep up, and of course, worse at low RPM

I would charge the battery and recheck. If it seems amiss, have the battery load tested. If you have a known good battery in another "rig" you can swap that in.

Post back with results