[bobH]

Here is how the factory did it. This diagram is copied from the 64 Ford factory service manual for a pickup.
Notice the resistor wire to the coil, and a 'jumper' wire from the 'I' terminal, that bypasses the resistor wire.
So, if there is no 'I' terminal (as per old 6V Fords), use the jumper wire, basically as shown, but connected to the 'big' starter terminal, and put a diode in it (to prevent running ignition voltage being 'back-fed' to the starter).