If you end up using a 12V tach and want to use a voltage reducer I think I'd spend the extra money to get what is known as a dash gauge voltage reducer or regulator instead of a simple resistor type. Don't forget to change the light bulb in the tach to a 6V one or you will think your eyes are going when you look at it at night.
The green trigger wire that connects to your distributer needs no modifications or add ons, just hook it up.
Mike
