there are single wire alternator conversions for 12c on 2n. but you won't be getting 12v from a stock 3 brush N genny even with the juice screw cranked...
if you want a 12v 9n/2n, eithe rmake the brackets or buy a kit.
hang the alt, get the battery, get the 2.5 ohm coil, keep the oem resistor.
if you go whole hog nd get ei, get it running on points first while doing the alt conversion.. then get the ei kit that has the coil blank off plate and lets you use a normal round coil vs the old style square coils and resistor (combos ).
my 2 cents anyway..