Blowing my headlights.... WHY

Just replaced or not, the regulator could be bad, especially if it's a mechanical one and not the later electronic one.

Reinstall the alternator and verify the wiring is right per the factory wiring diagram for your year and model. Check the voltage (manual says to use the blue or black wire on the ballast resistor and a good ground at a high idle of 1250 rpm), but the battery terminals will work just fine, especially if the voltage is high enough to kill the headlight filaments. Output voltage should be between 13.9 and 14.6 volts at 80 degrees F. ambient near the voltage regulator, .6 volts lower at 140F, and 14.9 to 15.9 volts at 20 below.

Don't have a multimeter to check the voltage? Harbor Freight usually has a cheapie electronic one on sale for around 5 bucks or so. For that kind of money one should be standard equipment in every tool box.

Here's the troubleshooting chart from the '76 factory manual. As you can see it indicates the alternator field is grounded (field wire, field terminal, at the connections, or internally) just like jos51700 says, or the regulator has an open sensing circuit.