Jeep Sump Float - Cleaning, and O ring or no O ring?

[Piston Broke]

The M201 engine rebuild continues and we get to the sump oil float and its support tube.  The float and cover were soldered together, so I thought I would just clean them in the degreasing tank and have done with it.  Having then read somewhere that all sorts of horrors can accumulate inside, I thought I'd better bite the bullet and unsolder the cover.  Turns out that whoever wrote the article was right and despite vigorous cleaning in the tank there was still a load of solidified gunk lurking inside.  So, if you're in the same situation and are tempted not to take the float apart, it really is worth making the effort.

I then found another article where the writer detailed replacing the O ring in the moving joint between the float and the support tube (with a photo of the O ring in situ as shown below, which I hope the author doesn't mind me borrowing for the purposes of research).  Nowhere can I find an O ring mentioned in the parts lists or manuals and the few people I have spoken to who have taken the joint apart have not seen one (and there was not one on mine).  However, there is a fair bit of end play in the joint when the retaining split pin is inserted that would indicate room for an O ring, and it would seem sensible to seal this joint as well as possible to ensure no air is sucked in to mix with the oil being fed to the pump.  Does anyone know if there should be an O ring or not?  I am tempted to put one in, figuring it probably can't do much harm and might do some good.

http://i1362.photobucket.com/albums/r683/HainesGarage1946CJ2A/29F57116-BCA3-4D3C-B3DC-6D0199C33DCB_zps5n7jyj0l.jpg

[Piston Broke]

Inserting the photo obviously didn't work, but the address will take you there if you're interested (many thanks to Haines Garage).