Stefano, sorry for the incorrect assumption.
Ryan, I took a quick skim through the '69 Engine PIM section I have, Section 6-1 Page 210 has the clutch options. There are OU/OS/OW... I think it should be the OU, but I didn't have time to verify the engine codes in there, so don't quote me on it.
I have a picture of my original fan clutch ink stamp in my thread here, I think you have a CO account:
http://classicoldsmobile.com/forums/...tml#post810643