65 Barracuda - No Charge from Alternator

OP had alt tested. It tested good.

The 3 volts out if the VR is suspect the 3 to 12 v into the VR is also troubling.

I would jumper from the battery to the input of the vr. That way you have a for sure 12v going into the VR. If you still have only 3 volts going to the field of the alt. Then you have a bad vr. If you have 6 to 10 volts going to the field then you have some issue with the voltage being supplied to the vr.