Spark plugs suitable for you aircooled Volkswagen
I use Bosch spark plugs: Bosch Super W 8 AC
I got the one pictured (and three more to make a full set) from Megabug at the Volksworld Show 2007.
I've also been told NGK 4210 B5H5 spark plugs would also fit my VW Beetle fine, but I couldn't get a full set to try them.