Having charging issues

A multimeter would make trouble-shooting easier. With everything hooked back up, disconnect the FLD wire from the Vreg and measure resistance from the FLD wire to BATT-. If you measure infinity, the FLD wire is broken, the brushes are bad, or the 2nd brush is not getting grounded to the alternator case, or you don't have a good return path from alternator case to BATT-. If very low (<5 ohm) the wire is shorting to ground somewhere or the field is shorting to the case. The field resistance should be around 10 to 100 ohm (I am kind of guessing).

If OK above, when running verify that Vreg is applying a voltage across the two field terminals (brushes). ~12 V is "full output". You need an ammeter to measure the true output. The path to the ammeter in your dash could be bad (common) or the ammeter itself. Try the "Mad Bypass".