BTW - That earlier GMC ring gear is listed in the 1950 Book as 838177. The GM Partswiki data base doesn't appear to have any books that list GMC part number supersessions or recessions like exist for some of the Chevrolets. Perhaps one of the other GMC gents with more parts books resources can shed some light on the earlier part number and if it was replaced by the generic GMC/Chevy one Bill provided???
