I got a new sending unit from Aircooled.net today and I noticed something that I can't explain. With the sender John included a gasket and replacement screws (which I think you usually have to get separately). There were also some washers - 4 nylon ones and one copper one. When I removed the old unit and looked at the original screws there were also 4 nylon or fiber ones and 1 metal one. Now I understand that the metal one is probably to make sure that it's getting a good ground past the seal to the tank body, but why not just use 5 metal washers? Why 4 nylon ones?
Anyhow that sender seems to work okay. I guess now I need to run very low on gas so I can see where it thinks the bottom is. :)