it has one black one black and green and one brown being the ground please help
Would have to look up wiring for a Cabby as I never owned one, but most Volkswagens do not get the tachometer signal off the coil. Yours I believe would be a Digifant II setup and the EUC would provide the signal. It would I guess go from a pin on the engine harness from the ECU to a connector in the area of the ECU, then through the fire wall into the relay panel abd back out into the instrument cluster. There are plenty of places where the contact could get broken so a wiring diagram would be best to use.
Noting that you are in California which would perhaps mean Digifant I -- the ignition coil nas a power stage (ie. special coil) which has a black wire at terminal 3/3 a green and black wire at Terminal 3/2 and a brown wire at terminal 3/1. There should also be a red and black wire at Terminal 1 on the coil. My thought would be that the red and black wire transmits a signal to the tach as that is the usual source of the tach signal. The wiring diagram that I have shows a computerized "tach control unit" in the cluster.
All that being said -- make sure that you have the correct coil (with the power stage) if you have a California (Digi I car.) FR