[BCA]

I just measured the resistor on a Mk2 panel: This resistor which stands alone without a fuse block, (unlike the Mk1 resistor which also has a fuse block) measures a bit under 1 Ohm. The trick would be have it in a running carrier and see if the voltage at the coil was about 4.5 ohms. Rob: you said your resistor measures 4 Ohms; chatter on other vintage Ford flathead sites suggest this may be too high and cause the coil to receive too low a voltage. When you get it all assembled and running then test the voltage at the coil and see if it is 4.5 volts.
It would appear that the Windsor Carrier and the T16 Carrier, both being 12 volt vehicles use a "voltage divider": 2 resistors on a mounting block (see Michael R's photo). Two chores are necessary: drop 12 volts to 6 volts for the gauges, and drop 12 volts to 4.5 volts for the coil (assuming the Windsor and T16 coils like 4.5 volts.) I can't prove this theory since the T16 wiring diagram is very poor and I do not have a Windsor wiring diagram.
The resistors on the T16 voltage divider are different: one is about 4.5 ohms and the other is about 6.5 ohms. If they are useful for other applications then I have them in stock..... Brian