The trigger is the points, grnd, self explanatory and 12 volt switched is for the light,your back indicates an 8 cylinder, if you pull the cup off there may be a slider switch inside to choose the number of cyl.s, 4-6-8.
Jalopy is right. With the stock wiring harness the trigger wire is green to telegraph the fact that it is never a 'hot' wire:
The Ranger Station - Tach Wiring.