It doesn't matter. Any of the flywheels will work because the om603 gets it's RPM signal from the starter ring gear, not the timing windows. 4cyl gassers have 2 timing windows and 6cyl gassers have 3 timing windows. Diesels have no timing windows. Later 96+ flywheels have 64 timing wibdiws. You can install any of the 4 types of flywheels on the om603 and your tachometer will work. Your diesel doesn't need an ignition timing signal for the engine to work. It just needs a speed signal for the tach.

Use whatever Sachs clutch kit was designed for you flywheel.

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CENSORED due to not family friendly words