Two of the three wires here are for the external voltage regulator that's mounted on the radiator core support, which will no longer be used once we're through installing the new Painless Powerstar alternator. The other black wire here that should be red is the alternator's current-output wire that sends all the power the alternator makes to the rest of the wiring harness, as well as charge the battery. | 
Here is the truck's stock voltage regulator on the back left side of the core support. | 
BEFORE getting started, disconnect the battery! |
Unplug the two wires and their plug; the dark blue goes to the field circuit in the regulator, which is joined to the alternator with the white wire. | 
Disconnect the current-output wire from its lug on the back of the stock alternator. If your battery was still connected, you would run the risk of the current-output wire arcing on the intake, fuel lines, or any other metal surface it might touch. | 
Once the three wires are disconnected, loosen the tension from the V-belt and remove the alternator from the engine. |
Feed the wires over to where the voltage regulator is for "simplifying". | 
I had to face my electrical fears by peeling back the covering on the stock harness next to the voltage regulator and figuring out what was going on. This was mostly for my own interest and to figure out where to terminate the other two wires for the regulator (the red power wire and a brown one that connects the regulator to the ignition switch). You can cut both wires and cap them off right by the regulator to avoid opening up the wiring harness. | 
If things are going as planned, you should end up with a similar pile as mine, which includes the old alternator, voltage regulator, and its wiring. Like I said, you can avoid getting into the harness, making the job even easier and stress free. |