Mark says, "I used a
tach from a 1984 VW Quantum TD and a tach equipped instrument cluster
from an 85 gas engine Vanagon. I removed the gas tach and installed the
diesel tach in it's place. "

Do not forget to swap the dynamic oil pressure control unit that rests next to the speedometer in the instrument cluster.  Its the small "L" shaped circuit board w/ an IC, capaicitor and some resitors.  Gas and diesel ones ARE different since the diesel one gets the RPM signal from the "W" terminal of the alt and the gas one gets it from the distributor, or engine ECU.  I found out the hard way when I replaced my speedometer w/ one from a gas Jetta and had to remove the cluster again!  The low pressure warning buzzer and LED will not flash w/ low pressure at 2,000 RPM w/ the gas board in!  Its easy to miss--they look almost identical.

Also, its easy to replace LEDs in the cluster (VW has them for a professional look) and the picture placard in the diesel cluster will just slide out and can be put in the gas cluster for that glow plug filiment pictorial.  Makes a neat job!

--Nate