Autozone?

One question remains: My 9N was converted to 12V before I got it, and I never noticed until I had to jump-start it, that it is positive ground. It occurs to me that the alternator probably won't like that. Should I switch the battery to negative ground?? Will that affect anything else?

It will look like this:

Since you have a side-mount distributor, you have two options, with a 12-Volt conversion... get a "true" 12-Volt coil, and NO ignition resistor is needed, OR use a "converting" resistor with the OEM 6-Volt coil.

Here's a diagram for a 12-Volt conversion:

If headlights are used, it's better to source the power for the headlight switch from the OPPOSITE side of the terminal block than shown, so the ignition switch is NOT required to carry the headlight current.

You can use a DIODE, as shown in my photo, OR an "idiot light" as shown in the wiring diagram, to limit or prevent current from "feeding back" out of the alternator's # 1 "switched excite" terminal into the ignition circuit. If you want an "idiot light", use that system, if you don't want an "idiot light", use the diode as their function is COMPLETELY interchangeable, and the diode is easy to tuck out of sight.

Just be sure to use the lamp OR the diode, as, if you don't, the engine will not shut off with the key AND there is a potential for damaging the alternator's internal voltage regulator or diode trio.