I bought some Mercedes CLK forged wonder wheels, 7J16 ET37.  I
understand these use the "small ball seat" 12mm lug nut.  Are there
14mm lug nuts of the same "small ball seat" type that would work on
the Vanagon?  Would perhaps Audi or Porsche lug nuts work?

See pic here:

http://t3technique.com/images/IMG_3666.gif

Vanagon nut on the left, Merc nut on the right.

--
Chris S.
Disclaimer: "Death and serious injury may occur"