The ballast resistor is just that, a resistor. When the gap is open in the distributor, you'll get full battery voltage. When the gap is closed you should between 7-12 volts. To test the resistor, use an ohm meter, not a volt meter. In
theory, the ballast resistor is designed to be either open or closed. It works or it doesn't. Voltage passes through or it doesn't.
If you're not getting a spark, it's probably the Mallory module. They have a nasty habit of failing; and it doesn't take much. I went through about 4 of them before I finally figured out it was the main battery switch. I know it's expensive, but replace it anyway. If that's not the problem, you'll have a spare. Eventually you'll need it.
Do you have circuit protection for the distributor? If not, you should install one. It's cheap and it works.
http://www.summitracing.com/parts/maa-29351/overview/
