Well, it's not quite possible to plug in the fuel level sender if the tank 
is in and bolted up. You can reach the sender from the rear of the tank, 
reaching up and into that "tunnel" where the air-cooled heater duct runs; 
but the space is just too narrow to maneuver that rubber-booted plug into 
place. The only way to do it is:
1) prop up tank at the center-rear. A good floor jack is best.
2) unbolt and completely remove the fuel tank support rails.
3) disconnect fuel return line only (feed line has enough slack to stay)
4) lower rear of tank about 2 inches
5) reach in, plug in sender
6) do 1-4 in reverse 

ugh.

-- 
John Bange
'90 Vanagon
"Keine Bange, wir holen die Zange!"