Transmission arms

No lock nuts, no loc-washers.
The factory nuts had a wide base on them which was serrated.

Any and all nuts that you install there will work themselves loose, and away goes your neutral gate. This happens because all these decades later, the interface between the studs and the levers, have rounded corners. The only fix is to replace both studs, levers, and the nuts.
But
I have a better idea that I have been using for decades.
What I do is; with trans positioned studs up, I put a couple of drops of light oil down the studs, then let that penetrate, then wipe the excess off somewhat meticulously. Next I clean the levers. then install them being sure they go to the right locations.
Previously, I have obtained the right nuts, or a reasonable facsimile with thick flatwashers.
Then I Red Loctite the cavities between the studs and the levers, this will turn to stone in a few minutes so nearly right way I Blue-Loctite the thread in the nuts and install them good and snug.
Right after that, I give the box a quarter turn until the studs are in the normal position, then shift them all.
And Finally, I come back every couple of minutes and shift them again.
It has happened to me that the Red-Loctite penetrated down into the bores around the studs, and it hardened there, making it impossible to shift. What a slugfest that was to correct. And so now, during a rebuild, I always smear that tunnel with silicone grease and problem solved. However, if the cover is already on, the above procedure has never failed me yet.
After this is done correctly, those doggone levers will never come loose on their own, nor will the nuts lose torque, and you may never have to realign your neutral gate ever again. My last time was 2004, at the last rebuild..
If you do not have the correct nuts, no big deal; with red-loctite, any correct thread nut will do, just put a tight-fitting washer on the stud first, to prevent bottoming the nut on the flats.

Oh I see I'm late to the party, lol.
No big deal, those First Responders got you covered.