Spent today upgrading the charging system. My battery charging issue was one of three things, alternator, wiring, or voltage regulator. So rather than test each, I just swapped everything.
I installed a brand new Bosch Nippendenso-style alternator along with an external regulator. The alternator, regulator, and pigtail for the regulator were all available from Rock Auto.
Since I'm using the newer style alternator and tensioner, I don't have to worry about getting a socket and extension through the adjuster hole in the core support on my Charger. So, I mounted the voltage regulator to the core support right by the alternator.
After burning a hole in the positive wire from the alternator with my hot radiator... I had already removed the positive wire from the plastic alternator connector. I decided to finish deconstructing the plastic piece with a hack saw in order to separate the alternator ground wire and the field wires. The field wires were getting replaced, but be careful not to nick the ground wire.
Here is everthing out of the plastic shroud. The ground wire keeps it's screw terminal. The green wire isn't used, as it runs to the internal voltage regulator in the SMEC. The blue wire is a +12v Switched source and needs to be extended to pick up one field connection on the alternator and the middle pin on the external voltage regulator.
Add some 18ga stranded wire, preferably blue, to the blue wire. Leave it long so we can cut to fit later... about a foot will do.
If you trace the green wire back in this alternator sub harness, you'll find that it terminates in a connector. Pull the internal keeper from the plug, and unlatch the pin that is soldered to the green wire to remove it from the connector housing.
Just in case you want to change everything back, you can tape the green wire/pin back along the harness to keep it out of the way. If you don't care, you can cut it off or remove the entire green wire from this harness. Either way we're just making sure the internal regulator in the SMEC isn't fighting our new regulator. Severing this green wire does the trick.
Now you can reinstall the alternator sub harness, and go ahead and make the connections to the new regulator. The blue field wire (+12v Switched) picks up one of the field connections on the alternator and then continues to the middle pin of the voltage regulator. Solder on a screw terminal to make the connection to the alternator. The green wire simply runs from the other pin on the regulator to the remaining field connection on the alternator. You can also see that I added a black jumper to run from the alternator ground wire to the body of the regulator. In theory the regulator is grounded through the screws holding it to the core support, but I wanted to provide some insurance.
Bundle those wire in electrical tape or friction tape to keep everything tidy and you're all ready to go.
Here's a diagram that might help anyone else doing the external regulator modification. It's not hard, but I had to review a couple sources to make sure I understood everything.