This assumes (as I always did!) that the four wire stators have three coils for the AC headlight and three for the rest of the electrics. The Snidal manual reckons it's FOUR for the AC headlight and only TWO for everything else, a quick check of my non-encapsulated stator wiring revealed that he was right - in this case! Would that have made a difference?
Given the availability of different aftermarket stators (Minda versus Swiss, or who knows these days?), I suspect you could have either four plus two OR three plus three.
In the wayback 4 wires exited the stator. Originally in the dim mists of time one pair of coils ran AC lights and the second pair ran thru a hi-tech (for 1960...) silicone rectifier to make DC for battery charging. A switched shorting system took care of Hi & Lo beams, a mechanical regulator took care of charging.
Way, WAY back the earliest Indian-built Bullets still had a Lucas MO1 magdyno for sparks and lights, these certainly would have had the old electro-mechanical voltage control or CVC boxes for the 6V dynamo.
On going over to the alternator, from all the wiring diagrams I've seen, they simply copied the standard Lucas 3-wire, 6V positive earth/ground package as used on (e.g.) my old BSA C15.
No separate voltage control unit on these, it just relied upon switching the coils in and out for full output for when the headlight was in use. The old 3-wafer silicon rectifier was standard Lucas kit on all alternator British bikes for years afterwards, even after the British factories went for 12V systems and zener diodes for the voltage control. The only un-rectified AC function on the 6V system was in the emergency start position for use with a flat battery, which allowed the alternator to power the coil directly, with a dire warning to turn the ignition switch back to the normal run position immediately the engine fired up, or else! Not sure if Enfield India ever incorporated THAT feature.
By the time Chennai went for the 4-wire AC headlight thingy, Lucas had been producing three phase alternators for some time, as well as higher output single phase alternators. Something like this would have made more sense if the old alternators were getting a bit weedy, the new ones had the same fitting, but no, let's confuse as many people as possible with two separate systems on the same bike. I think the penny dropped with the 500 AVL models, and the factory has been fitting Japanese-style 3 phase (permanent magnet) alternators on all new models ever since.
Someone, somewhere knows exactly why a separate AC headlight system made sense. I would have thought that a battery-independent IGNITION system would have been of greater value. The factory also thought of this with the CDI ingition used on some of the home market 350 models, but say hello to the SIX wire alternator...
A.