Msd 6c
Better late than never?
From MSD:
No. It doesn't SHOW the pin in question. That output
IS the tach, as already stated. I am running the 6C box in my Duster.
I don't see something on the pic of your 6C that IS on mine: I have red/black wires connected directly TO the MSD box. They are power/ground. My 6C is mounted on the left fender, power comes from the starter relay connections (battery is in the trunk).
My 6C has performed flawlessly for over 20 years.
Good luck!