A two wire (also referred to as a three wire) is the one you want to use because it will begin charging as soon as the engine starts. A 1-wire alternator typically needs about 1200 rpm engine speed to excite and begin charging. Because our old trucks do not idle that fast the charging will not begin until later. You will notice the symptoms as being much like the generator you took off....

The wiring harness you are looking for is called a DA Plug and besides helping the alternator to begin charging when the engine starts it also makes the engine shut off with the original ignition switch. Because an alternator is able to produce current at idle it will flow backwards and keep the coil hot even after the ignition switch is turned off. The result is the engine still keeps running even with the key off....a big source of social embarrasment!!. That is why ignition switches were changed to the "accessory type" in the 1960's. They could use the accessory terminal to isolate the alternator terminal from the rest of the terminals on the switch thus stopping the flow of current back to the coil.

Fifth Avenue manufactures the DA Plug and they are also thru various dealers.

Thanks Randy

Fifth Avenue Internet Garage