As I stated above, GM chose to use a coil that functions correctly with about a 9V input. That assures a hot spark during hot and/or cold starts with lots of load on the battery. To prevent point damage during normal running a resistor is used in series with the coil primary winding. Points can handle a maximum current flow of around 5 amps, but they're much happier with 3.5-4 amps. Choose a coil primary resistance and a resistor that keeps the primary current somewhere in that range, and bypass the resistor during starting. How you do that is subject to all sorts of "opinions"- - - -those re like noses- - - -everybody's got one and they're usually smelly!
Jerry
