With the trans uninstalled, the input shaft is missing one of it's support bearings (the pilot bearing in the end of the crank). So it's not too much of a worry if it's a little wiggly.

I pulled the top off my junkyard M41 (to swap to the long shifter style) before installing it in the PV, and missed the subtle fact that two of the syncro cones were cracked. So instead of just looking at the gears for wear, also try to examine the state of the syncros as well as you can. In my case there wasn't anything missing, so a casual examination wouldn't have spotted it. What I would have needed to do is poke at all 4 syncro cones with screwdrivers as I rotated them around to see if they were cracked. Sure beats installing it and then finding out you need to pull it out again...

I'm sure the ODGuru can reccomend some OD maintenance while it is so accesible too.
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'63 PV544 rat rod, '93 Classic 245 + turbo