Assuming there is a difference in the position of the pick-up triggers on the MC18 and MC21 flywheels (in relation to the crankshaft), then to keep the timing standard you have to run the MC18 flywheel with the corresponding MC18 PGM (be it PGM-I or PGM-II) and run the MC21 flywheel with the corresponding MC21 PGM (PGM-III)

But the whole point of this thread is to find out exactly what the difference is between the MC18 and MC21 flywheels in terms of the ignition timing triggers.
I would like to know, because, it may be possible to advance or retard the ignition simply by swapping flywheels.
This in combination with offset woodruff keys may make quite a few different offsets possible in terms of ignition timing.

So back to the original question,... does anyone know what pick-up trigger difference there is (in degrees) between MC18 (R5k / R6k) and MC21 flywheels?