Battery fried and more

We disconnected the field wires on the alternator and the battery would be steady at just over 12v. We discovered that this would also happen when you would hook up the positive field wire BUT NOT the negative field wire. When the neg field wire was disconnected, the battery would be stable around 12.3v.

Let us make this clear:

Are you saying that with only the blue field wire hooked up the voltage overcharges?

IF THIS is the case, you have a problem in the brush holder / insulator, or a short in the actual field winding in the rotor.

TO make sure:

Unhook both field wires, motor off. Check continuity from each alternator field terminal to ground. It should be infinite, that is "no" continuity

If there is continuity, the alternator has a problem