charging system trouble

Voltage regulator is rectangular in shape and has a screw connection for the field terminal and a slip on type connector for the other terminal. Spade connector i think they call it. The new one is the same type. I did the voltage drop test. I have 1.5 v at the ballast and/or field on the alt. I've been checking connections and even replacing wires 1 by 1. No change. I hooked up an alternator i had bought that is for a 71 fury and the voltage dropped to .09, i think. Didnt write it down. I dont know if this alternator is compatible with the system on the 64 dart. It looks a lot different. Could old wires and the resistance they might draw create such results? Theres not a lot of wiring between all these points. could it be the alternator? It was a guess that it was good when my friend gave it to me.