My 1990 Dodge with the 5.9 Cummins did not come with a factory tach. There are after market tach set ups that have you put a magnet on the crank sprocket with a sensor mounted to count each pass of the magnet. that may be an option for you.

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K