Mystery Part in Transmission Pan

Well, technically this is a question related to my 68 cougar, not my Ghia, but I'm confident II folks are smarter than the 5.0 crowd simply because they own II's. Anyway, I'm in the process of doing an AOD swap and when I pulled the pan off the AOD tonight, I found a small, tan, plastic mushroom-shaped part just lying around in the pan. It's about an inch and a half long, half inch in diameter and has an o-ring around the mushroom head part. The "stem" part is about an inch long and about quarter inch in diameter.

Any ideas what this is and where it should really live inside the tranny?

Thanks guys. Someone should sue Ford over that for intentional infliction of emotional distress.