Not entirely sure where you're going with that question!
Based on the info you provided, you have MC28 engine cases in an MC21 chassis (well, frame at least). There's no difference between the later MC21 cases and the MC28 cases. The MC21 GPS (gear position sensor) will have been fitted in place of the MC28 neutral switch to enable the PGM-III to operate correctly.
Running an MC28 with MC21 clocks is a completely different question, and an entirely different kettle of fish!
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Andy.
NSR-WORLD.COM
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