[RichardJ]

I found this image on the internet years ago. As you can see, they used the shortcut version of the wiring that many use when installing an internally regulated alternator. The DN shown is wired the same way and is how yours is wired.

In the images, both the DN and SI wiring have TWO wires coming away from the respective Alt/Regs. Both have a Red Battery wire and a Brown exciter wire that goes to the ignition switch. Your white wire is an obvious rewiring job and you will have to trace it yourself. The junction of the several Red wires that VetteVet is showing you was buried inside the original harness.

If you are still using the original Ammeter, that junction is fairly important. You can see the black and grey wires with fuses in the VetteVet drawings. Those wires go into the Ammeter. The large Red wire that connects the Black to the Grey wires has two purposes. The second purpose is to act as the shunt for the Ammeter. If that Red wire is too fat or too short, the Ammeter will read too low. If the Red wire is too small or too long, the Ammeter will read too high. The resistance of that Red Battery wire was calibrated so that the correct amount of current would flow through the Ammeter and give the correct reading.

The external regulator is labeled "F",2,3,4. Regulator wires F & 2 go to the Alt and nowhere else. On a conversion to Internally Regulated Alt, the F & 2 wires disappear inside the Alt, never to be seen again.

The #4 Exciter wire on the old Reg plug, is moved to the #1 post on the Int Reg and serves the same function.
The #3 Sensing wire on the old Reg plug, is moved to the #2 post on the Int Reg and serves the same function.