Fuel tank sending unit
Huh, I just went to the Plum Krazy site, and the unit they are selling with that part number looks exactly like the one everyone else is selling, with the little short arm and the pivot point halfway down the tube. Image here:
The factory A-body unit had the pivot point up near the exit pipe, with a very long arm, similar to this photo (but this one isn't correct, either, because the sock is straight out instead of at a right angle).
Keep looking...