Here's another piece from the "Sultan of FC's", Jesse Ybarra on the electrical power needs of your FC Jeep.
The cons first
6V or rewound to be a 12V generator is still a generator, it generates amps at the higher rpm only, it does not charge the battery at idle, at Idle or slow speeds, even the generator converted 12 V system, will not maintain a battery to be kept charged, if the lights are on for extended periods. The other more important negative issue, I have, is that the points, contacts, in the external mounted regulator, is an unstable voltage controller, it is affected by temperature expansion and rust deterioration because of humidity, the wiring and connections to and from the generator and regulator, are also additional problem areas. Generators require more engine torque to rotate, than an alternator. Use of a generator with either the 6 V or 12 V to a starter will cause additional heat to a starter, because while cranking, it pulls only juice from the battery, example, a vehicle with a 12V generator at cranking is really only cranking at 10 V, what this means is that it needs to turn quickly, and start or the starter will get hot, even when everything is working at it's best. So a starter with a 6 V or 12 V generator is requiring a higher amperage, thus creating higher heat= more wear and tear to the starter.
With 6 V or even with 12 V at slow Idle speeds of the FC-150, the headlights are always going to be dim, putting on the blinkers with the radio on, while waiting for a signal to change while the lights are on and the heater is on, will discharge a battery enough to where the turn signal will not blink.
Generators are becoming extinct and are expensive to rebuild. Original equipment or not, it is a bad thing to have to call triple AAA because the battery is dead or starter is hot, and won't start.
12V alternator installed, is near impossible to be seen, as being non original. how many times have you had someone look at your truck and then want see the generator, how easy is it to be seen? The alternator is always going to be able to be purchased as an on the shelf item anywhere. The alternator has an internal built in regulator, and can be bought with a variety of 45-110 amp output. The GM Delcotron 1 wire alternator is almost half the size in length of a generator, this means 1 single wire to a 12V source, to connect it, to your system. This is my favorite, I run the same Delcotron, in my 1956 forklift, it has the 4 cylinder flathead Hercules.
NippoDenso alternators are even 1/3 smaller, they are popular also, so there really is no need to cobble anything up. Aftermarket brackets for mounting an alternator, do not destroy the ability, to return the truck to the original equipment, remember, you can save all the pieces and always go back to a 6v generator.
An Alternator, as it is energized and rotated while starting, immediately creates 14 .5 V at high amps. An alternator requires almost no energy from the motor to rotate compared to a generator. with an Alternator bright lights instant starts, 12V accessories are possible: electric radiator fan, electric fuel pump, electric winch, phone charger and many other items.
Remember none of these aftermarket items are cobbling or hacking up an original truck, it is still an original truck, no matter how original a truck is, nobody sells cans of 1957 Air, for the original tires or rusty water for the radiator, what is important is that you the owner is able to drive a narrow track, rather than have it in a museum parked to keep it from having 2011 dust settle on it.
An FC should be what you want for you not what is expected by others, I own vehicles that please me, I don't have to be a people pleaser about originality at this point I feel there is a larger list of people that have commented, how they would have kept my M-679 Ambulance original, And I feel that if those people can have an original M-679, I wish them the best.
I hope this helps,