Hello,

Daerr offers auxiliary fuel tanks for Syncros and
2WDs. They are made of stainless steel. Two
sizes are available: 67 Liter and 75 Liter.
The tanks can be mounted under the floor near
sliding door or opposite side. With the stock
and two aux tanks you're able to carry about
200 Liter fuel on a Vanagon without loosing
luggage space.

http://www.daerr.de/kfz/tanks.htm

Vanagon aux tanks you will find very down in last
table.

Regards
Helmut
'80 Vanagaudi