If you call an MB (dealer) parts desk with your vin they can give you your engine #.
This is where it specifys the relationship between your engine # and the correct part:
http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1FX0MB1RS1V90WC2SL&year=1986&make=MB&model=300-E-002&category=F&part=Distributor+Rotor+Adptr&appEngines=_any
In the pictures there appears to be a flange in the end of one version that I begin to suspect is causing the sticking.