Lonnie,
Regarding your questions:
1. The bracket is/was unpainted, galvanized, I think.
2. The negative terminal goes to the distributor. If the coil primary connections are reversed, you will be firing the spark plugs with a positive voltage on the center electrodes, which will increase the firing voltage about 10%. You probably won't notice the reversed polarity until the spark plugs begin misfiring under full-throttle acceleration, after the gap increases with mileage. With the 6-volt system, you might also have some hard cold starts in cold weather- below zero temperatures. And, rest easy, your truck won't self-destruct, or blow you up, if you wire the coil incorrectly.
3. There should be a ballast resistor in series with the coil if the system was properly converted to 12 volts, but some 12v coils have internal ballast resistance. Measure the primary resistance of the coil: with internal ballast resistance you should find about 3 ohms, maybe a little more; without internal ballast resistance, the primary resistance should be around 1.5 ohms, plus couple of tenths is alright, but minus not much.
If you are back to 6-volts with the electrical system, you shouldn't have a ballast resistor, nor the coil with internal ballast resistance.
You can use the 12v coil if it does not have the internal resistor, but a 6v coil would be better. If the coil has internal ballast resistance, it should be marked on the case with something like "Internal Resistor", or something similar.
Hope this helps.
Harvester
