On my 57 Skyliner I have an alternator, a Motocraft, maybe a 3G. Anyhow it has a wire that goes to the GEN light in the dash. As I understand it, the alternator is first energized by the generator bulb through that wire. That is all good except what happens when the bulb burns out? That would be a poor design to rely on that. So I located a wiring diagram and indeed that bulb should have a 500 ohm resistor in parallel with it. I will check my car but I would imagine that resistor isn't there as it wouldn't have been part of the original setup. I will be adding a resistor.
I can`t speak to additional resistors, but I have had a Motorcraft 3G 130 amp alternator in my 59 with a 428 for 5 years now, and it works fine, and the GEN light in the dash functions as it should, so I have never added anything under the dash. IF the GEN light ever burns out, I will just replace the bulb.
Yes they are a great alternator. I posted this because if one were on a trip away from home, a failure of the bulb would prevent the alternator from working, as I understand it. When they were used as original equipment, I would say that they had the resistor in parallel with the bulb. I am going to wire mine in under the hood.