[TitoElSpicco]

green - negative side of coil
white - interior lights
red - constant power
black - ground

 

[TitoElSpicco]

There is something wrong with all stock tachs.. in the higher RPM's they can be as far off as 600 RPM's.
Mine freely revs to 7800, when i know it cuts off at about 7000..

 

[TitoElSpicco]

Step 2 - Buy a Haynes or Chilton's Manual
Step 3 - Look it up.

 

[TitoElSpicco]

don't look at where ford hooked their tach up, cuz christ knows what the hell they were doing.. find the part of the book that shows you how to install your coil, see which wire they say is the negative (or the ground) for the coil, and splice it to that.