I believe all versions of the M41 remote shifter interchange to the top of the gearbox. Lengths of the remote may vary depending which model car it was installed in (early vs. late model 1800 and later 1st gen. 140 series)- I don't remember.

You may find that there is a difference in how to engage reverse on certain versions. Though the gearboxes are the same, the method of engagement may be different. IIRC, early 1800 models had to lift the shifter to get into the reverse gate. While others simply moved the lever to the left against a lockout spring device that is located on the underside of the gearbox cover.

What model are you talking about?
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"Differences of opinions should be tolerated, but not if they're too different' - Sharon Craig