Thought I had a rusty tank in my '84 GL so I dropped it out.  Turns out it
wasn't rusty at all.  Thought I would share my procedure for this with the
list.
1. Unhook supply and return lines (one either side of tank) and drain fuel or
siphon fuel out of filler hole (quicker).
2.  Undo the two bolts (13mm) that hold the metal straps  to the front frame
of the van.
3.  Remove straps by pulling the tab in the rear of the strap out of the slot
it rests in.
4.  Rear of tank will drop down.
5.  Remove two lines from the side of the tank that go to the expansion tanks
above front wheels.
6.  Now pop loose the other plastic expansion lines from the top of the tank.
7.  Pop the small line that hooks to the filler neck (overflow line) out of
the tank.
8.  Unscrew the three screws that fasten the filler neck into the body and
push it into the tank farther so you can move it over to the wheel well.
9.  Pull out the filler neck.
10. Tank should drop straight down.
11. Unplug sender.
Reinstallation is reverse of removal except I would undo the one nut that
holds the expansion tanks in the wheel well on both sides so you have more
line to play with.  Also when reinstalling the expansion tank lines remove the
rubber gromet that seals them to the tank and pop this into the tank first
while you have the tank out.  Alot easier than trying to pop these lines back
on with the grommet still on the lines (tried this for about 20 mins and gave
up!)
You can use some vasoline for lubrication if necessary.
You can remove the overflow line from the filler tube and install it prior to
putting the tank back in too (make sure it doesn't fall out when you put the
tank back up like mine did.)
Also on reinstall tilt the tank so that you can get the front of it under the
lip in the front beam and then just push it up so it is level and then you can
slide the end of the straps back into the slots without a problem.
Have fun and I hope this helped somebody besides myself.
Ken Wilford
John 3:16
PS I wrote this up because I couldn't find anything about this in the
archives.