I removed and repainted the tank on my '74.  I painted it red.

Don't know if the Vanagon tanks were made this way or not, but the Manchester
tank on my '74 Westy has metal tags that are just tack welded at the corners
allowing water to work under the tag and rust out your tank.

My tank was in good shape so I sanded, primed and used a non shrinking spot
filler to seal around the edges of all the tags.  2 years later all is still
well and rust free.  You could drain the tank and weld up the tags, but quite
a bit more work.

Steve Lashley
'66 Westy
'74 Campmobile
'93 EV MV
http://EuroCampers.com
314-614-0750
Importing German Side Tents, Fiamma and Paulchen bike racks and other
accessories for
Bus, Vanagon and EuroVan