europa s2 1969, the "T "after gas pump ??

[Sandyman]

Resealing the sender unit could be an issue with the tank in the car.

[GavinT]

Is it though?
Perhaps a wisp of Hylomar?

Probably a good idea to have a spare cork ring/gasket on hand . . . and that giant ring holding it down is rather archaic, but there's surprisingly little force required to remove it.
It looks more daunting and scary than it is.

Lots of info in this thread.
http://www.lotuseuropa.org/LotusForum/index.php?topic=255.0

Here's a (stolen) pic of another home made ring removal tool.