[steve s]

You will discover that there are strong feelings on every side of every Model A related issue. Decide what your "concept" is for your car and do what it takes. In this case, if maximum authenticity lights your fire, stick with 6 volts--many people are happy with that. If the APPEARANCE of authenticity is good enough for you, then you nave more options, including 6V voltage regulators either built into the cutout can or hidden in the generator, or an alternator built into a generator case. If reliability, convenience for use with modern accessories, and peace of mind is a priority, then join the rest of the world that has switched to 12 V, negative ground: there were good reasons for going to 12V (by contrast, negative ground was apparently just a technical toss-up but done for uniformity's sake.) I've done the switch but not with a kit. The kit you describe sounds complete except for a load resistor to put in series with the horn. I don't know what the rectifier would be needed for.

Eventually, you'll have to confront similar issues, like detergent oil, thermostat, fuses, antifreeze, sealed water pump bearings, shortened Pitman arm, and on and on.

Have fun!

Steve