AL,

The closest thing I could find to this, at a quick glance, is the older '60s Autolite (or Leece Neville) alternators with the external regulator & a charging light. The schematic indicates a 15 ohm resistor wired in parallel with the charge light. One side is wired to the ignition switch, the other (eventually) to the field current supply diode. I've yet to figure out the whole nuances of the regulator, it's kinda goofy (I was raised a GM boy & converted over in the '90s), but this would seem to go along with your memory. The bulb being dead shouldn't cause the alternator to stop charging, UNLESS the resistor was also burnt out (so the bulb formed the only circuit). The setup for an ammeter is slightly different & has no resistor, & the field diode is basically hot-wired (eventually) to the battery post on the starter relay. The ammeter is wired in a totally separate place & does not represent either a load, or voltage, to the supply diode. This method is similar to the 10SI version I described earlier.

At any rate, we can possibly assume this general approach was used by Ford into the '70s, until the external regulator was eliminated. Dunno about Mopars, but '60s/'70s GMs are different, at least what I've worked on.

So, the next step, I reckon, is to find out what charging system Todd has current-ly. (Yes, I know, that was bad. ) The original '53 setup wasn't wired like the later system I just described. With any luck he has one o' them newfangled internally-reg'ed alternators & can wahr it up diffrunt if needed.

"Shocking. Positively shocking."