Jim, Jim, Jim,like so many Vanagon parts, that tank really dosent need
repalcing. A new tankfull of your favorite gas will probably dilute the
crud.Just dont let the level get so low,again. Remove the fuel filter,cut
it open, and look for that sock,inside there.I think it is a size 6 thur
10 tube variety.White with a grey heal.It could be in the high pressure
filter ,downstrem from the pump, by this time.  My coat hanger zapped
something several times when I stuck it inside.Got big and mean flakes
inside the filter.A hand full of them.

Removing the gas tank is never fun. Got to remove the filler tube,the trim
piece where the gas cap(remove the 3 screws and rotate it about 25
degrees) is and the return line.All those expansiuon tank lines need to be
coriographed as the tank comes down. The Vanagon needs to be raised , as
the straps need to swing down ,to be removed( 13mm).Then the tank needs to
be Jimmied.