Just found this - haven't called yet (it's Sunday!) but they claim to be
able to take your steel centers (spiders) & weld on their rims - even 15"
rims on 14" centers!! + custom offsets!!  They're biased toward US iron &
commercial app's, but I'm still gonna find out ref Vanagon rims

http://www.stocktonwheel.com/

Also, one of the best take-off sources is Acker Wheel in San Jose:

http://www.ackerwheel.com/

Austin