Doesn't Charge enough!

12.3 to 12.5 is not charging.
Charge voltage should be 13.5 to 14.5V

Take a close look at all the wiring at the alternator and voltage regulator for a loose, frayed, burned, dirty, corroded or broken wires and connectors.

Put a jumper wire on the wiring on your plug going to the reg. Pull it it out, and jump the two outside wire. You should see a huge jump in voltage. Don't hold it it there though lol. That is the alt wide open. It that works, the wring and Alt is fine. It's the reg. But here is something missed. Grounding the alt is not just grounding like an engine. You MUST ground it with the stud marked"GRD", or it won't charge. The voltage will barely move if it's not grounded there, AND everything will test correctly like what you have going on there.