Interesting ballast resistor article.

Rice Nuker said
It seems there is a lot of mention that the coil is the one that cannot handle the 12 volts. The factory coil cannot handle it for long and neither can the Mopar ecu handle grounding (triggering) the factory coil load when you switch the coil to 12v.

I'm not 100% certain that's correct, but it probably is.

So, even if you switch over to a 12V coil it has to have the correct resistance sum to operate with the mopar ecu.

A lot of coils listed and marked as "12v" or "Use without coil resistor" have a ballast resistor inside the coil.

An hei can trigger a 12v coil because you are supposed to select the appropriate resistance coil for the hei module and the hei attenuates the grounding (triggering) and regulates dwell automatically (based on rpm I believe).

Yeah, there's good discussion of the workings of the HEI vs. Mopar electronics here.