Sal,
Why do you need a ballast resistor?
Well, just because (if you are using original style points).
I am sure someone will post all sorts of logical/technical/mythical reasons why GM (and maybe others) had/has this requirement, but, just be sure you have a resistor or you will burn out points.
You can either put a ballast resistor between the ignition lead and the coil, or, use a coil that has the resistance built in. Some people say use the resistor (rather than a resistor coil), so you can wire the starting circuit (to the coil) to run at a full 12v, and then once you have started, you run through the resistor to the coil.
