3B, so after doing some research, you're correct that GM 3686530 cross's to National 6358, however so does GM 3681195 posted by Mike B. I went to Rockauto and searched both GM seals and both returned to SKF 31870. Went to National's site and used the SKF 31870 which crossed to 6358. So apparently both styles of Hubs use the same seal. I've always thought the research is half the fun working on old stuff.
Thanks
