[RichardJ]

VetteVet, in your earlier post you are showing the 10 DN (Ext Reg) alternator with the resistor going to the Acc post, but on the 10SI (In Reg) you are not. I think that may add to the confusion. You did say, "the diagram with the idiot light and the Accessory wire feed to the fuse panel is left out but it still is in the circuit". I assume this qualifying statement is to let people know that the original resistor is still in the circuit, but by omission it makes it vague and confusing.
I like this drawing a little better because it helps to shows that nothing under the dash needs to be changed when converting from the DN to the SI alternators.

Fixit-p, I changed your drawing a little. Voltage on terminal #1, is connected to one side of the field, but it also biases TR1, turning it ON. In order for current to flow through the field, it needs a ground and it is supplied through TR1.

I think we're going to be in some disagreement over the roll of the resistor that is in parallel with the indicator lamp.
That resistor has one primary function. If the lamp fails, the regulator and generator will continue to function normally. If you didn't have the resistor and the lamp went bad, you would have an open circuit. The resistor completes the circuit if the lamp is bad. The resistor allows a different voltage on each side of the lamp so that the lamp will glow when there is a generator failure.

I don't know if the "resistor limits current flow to from the alt protecting the regulator or diode trio" as fixit-p said. It INCREASES current flow to the regulator.
You know,,, two resistors in parallel (resistor and lamp) have less resistance than either, alone.

If you use the lamp and no resistor the Alt will not begin to charge, but the lamp will glow. The voltage at terminal #1 will be too low for the field and TR1 will not be turned ON. The Alt has some residual magnetism. so you must rev the motor high enough so that the diode trio can provide the current necessaryfor the Alt to begin to charge.

If you are wiring from scratch or don't have an Acc, ignition post such as an older truck with DC generator you can wire a resistor directly across the lamp.