I used an Autometer Tach Adapter Model #9117.
You will need to cut the wire that supplies power to ALL four coils and insert the tach adaptor.
This wire can be found in connector C133 pin 5, the wire is Green-Orange, the connector is located next to the left headlight.
You will need to cut this wire between the connector and junction S108.
S108 is located on top of the engine and then branches to all four coils.
Dave