I want to hook up a factory tach in my '70 bird. The cluster is from a '71 and everything else works as it should. I believe my '70 Espirit may have not came with the tach option when it was new. I need to know what the pinouts are on the white plug that pertain to the tach functions. I know there's the wire off of the ignition coil but don't know where that goes from there. I have a '78 shop manual and it shows information for the regular gauge package (with out tach) but doesn't go into depth for the actual wiring for the tach itself.