This may be a better option:

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1CQ0J3JZ41OD0SSSB2&year=1981&make=MB&model=300-SD-002&category=All&part=Glow+Plug+Kit