[Excaliber]

Very few cars, these days DO include a ballast resistor. It's function is handled by an electronic type ignition control module. But what your doing is like an old school point and condensor type wiring, no electronics, just wired straight to the battery with the negative wire acting, as it were, "the points". A mechanical switch that makes or breaks the current, with a condensor that helps to limit arcing across the point contacts which would lead to burned and pitted contacts.

SOME coil's have an INTERNAL ballast resistor, some require an external one. Often, with todays modern coils designed to work with electronics, they do not have nor require an INTERNAL resistor. A resister can be purchased from any neighborhood parts store. They all serve the same basic function, reducing the voltage from 12 to 6 or 7 volts. It really doesn't matter what vehicle you have, if it came with points, it had a resistor OR (like GM) a resistor WIRE included in the wiring harness.

12 volts to a coil without a resistor will burn up the primary wiring inside the coil, you will not see the damage.