i've had problems with the ignition (1941, is missing terribly, almost undriveable) after the engine warms up. have installed rebuilt helmet distributor and a new coil from one of the aftermarket vintage ford outfits. didn't help and now am not getting no spark at all. ...i suspect the new coil has been fried. so basically a waste of time and money.
my next step is to install one of those adaptor kits that permits the use of a slightly more modern canister type coil (which i bought a while back from e-fire) while still using the helmet distributor. ...we'll see how THAT works.
FYI, still running the positive 6v system. don't know if there's an artificial resistance added (aka ballast resistor?) when the engine is running, but absent when starting. which is how i understand that it works.
in any event, i plan on running a wire straight from the battery to the new canister (so as to bypass any ballast resistor in the wiring) style coil and then to the adaptor cap that is part of the kit.