Voltage Regulator problem

Sorry for long post. 73 Duster originally a /6 but swapped to 318 and 904 before I got it. Went to start it the other day and battery was dead. Put it on the charger and got it started. Put my digital voltmeter on it on got 12.6. Drove it around a bit then stopped at the parts store to have them test the battery and alt thinking I had a bad battery. Test said battery and alt were fine but voltage regulator was bad. Looking around I found this. reg.jpg
Voltage regulator bolted to the firewall but nothing hooked up to it. Thinking I had somehow knocked the plug off at some point in time looked for it to hook it back up. Nothing. Cant find a plug anywhere. This is what the alt looks like.
alt.jpg
Has someone before me converted to 1 wire alt?