I don't believe the old/new style pump issue is applicable to 617s, I think it's one of the 60x engines, is that correct anyone?

However, I did have the original vacuum pump on my 617 fail at about 325K miles, causing a bunch of collateral engine damage (about $2500 worth). Mine failed in the middle of a long drive without warning (that I could hear at 80 mph). If you are hearing something from the engine, try to locate the source before you start replacing parts, it could be something else altogether.

This is the replacement pump (depending on engine number):

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1CQ0J3JZ41XJ1CW1K9&year=1979&make=MB&model=300-TD-001&category=All&part=Diesel+Vacuum+Pump&appEngines=_any

These are rebuild kits for the pumps:

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1CQ0J3JZ41XJ1CW1K9&year=1979&make=MB&model=300-TD-001&category=All&part=Vacuum+Pump+Repair+Kit&appEngines=_any