Mopar voltage regulator for race car

The only Ignition "On" I have in the engine bay would be the + side of the coil. I was worried about voltage greater than 12.5. Is that possible?
No no no not with MSD. If you are running a CD NOTHING and I mean NOTHING else should be connected to the coil except the two MSD box wires Not even the tach

Whatever you are using for a switch to get "run" power out into the engine bay is what I'm calling "run" or "switched 12V"