Modern Tach won't work with points?

[tubman]

I think switching to a 12 volt coil (and changing the wiring accordingly) will work. There are 2 electrical feeds needed by the tach. The tach logic itself is designed to use 12 volts. But the signal coming from the distributor (green wire) has to be 12 volts as well. I have been there and done that. We at first thought that the voltage of the ignition signal "just had to be there", but soon found out that it also has to be the proper voltage and polarity.