65 Barracuda - No Charge from Alternator

If the alt tested good, then it is most likely the voltage regulator (VR).

With the engine running check for voltage to the bottom terminal of your VR should be battery voltage. Next check for voltage at the top terminal. It should be 6 to 10v if the regulator is working properly, battery voltage if it has failed closed, 0 volts if it has failed open ( most likely)

you should double check that you have a good ground to the VR.