I have acquired a J-type M41 to upgrade my 142 with M40. The M41 is complete, sealed and fluids are clear but is in unknown condition.

How should I proceed to confirm transmission and OD health before doing the swap? Should I preemptively replace seals/gaskets or other wear items?

The M41 has the shifter relocation tunnel but I want to keep the original 142 funky/cool long shifter. Any caveats for this plan?

TIA,
Craig in SD, CA

The swap to the long shifter is straightforward. Having the cover off will allow you to look for any chipped gears. I don't recall if the reverse light switch is located on the shift extension--if so, you'll have to mount the old style that has the contact behind the reverse shifter rail. That should also be a straightforward swap from your M40. If you need one I think I have a few good used ones. The M40 cover may be already drilled for the fourth gear OD contact--if not I think you'll see a a flat boss where it should go. The transmission removes/installs easy enough to just go ahead and stick it in to see what you have. -- Dave