You might as well start checking out the retrofit. The law is Federal and implementation by states is spreading rapidly. Later model VW's had it built in; early models have an overflow valve but it won't pass as 'automatic' since you open before filling & close when full.
It's my understanding -- haven't checked out having it done to a Westy yet -- that it involves changing the fill valve and isn't that expensive. It should be little different than changing the millions of BBQ LP tanks going on every day. And since it's cost effective to change them, it should be cost effective to retrofit the VW tank. As frequently stated elsewhere on this site, the Westy tank is a generic US MADE LP tank by a company (Manchester) still in business. Go to an LP specialist like your regional distributor, not the local Quickie-Mart. Or call Manchester.