That is the idler arm and you will need one of these: http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=2D30S2O9Y2D30S33P1&year=1985&make=MB&model=300-DT-001&category=M&part=Idler+Arm+Repair+Kit

About the only special tool you should need is a long drift punch to drive the bushings out of the ends. (Use K-Y jelly to install the new ones.)

__________________
Sam

84 300SD 350K+ miles ( Blue Belle )