The blue foil on the back of the Vanagon instrument cluster came in at
least nine (9) different versions! The differences are small or large
depending on the year and model. Due to the number of variations a truly
comprehensive chart of wiring changes to mix clusters between the years
is not feasible. Jim Thompson has put together a reasonable document for
some of the clusters commonly swapped in. There are some errors in the
text of his document but very useful still for putting a watercooled
tach cluster in an early watercooled van that did not come with one.

http://www.oldvolkshome.com/late_van_cluster_install.pdf

Mark
(with all 9 foils mentioned above in my workshop)