This should be in the "Car Audio" forum. http://www.peachparts.com/shopforum/forumdisplay.php?f=10



Antenna switch picture:
http://catalog.eautopartscatalog.com/mercedesshop/sophio/image.jsp?title=Antenna%20Switch&url=http%3A//img.eautopartscatalog.com/live/P300511822OES.JPG

You should get the correct unit for your car, not alter the car to accept the wrong unit.
Search the "Parts" forum, someone should have the correct one for sale cheap.


PART NUMBER SEARCH RESULTS WITH PRICES
Vehicle 1979 Mercedes Benz 240D
Part: Power Antenna
Note: W/o Mounting Hardware
Does not include cables, antenna seal, or associated hardware.
Z4002-60138 Power Antenna Hirschmann IN STOCK $235.20

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1UH0TIW001UR16OMG4&year=1979&make=MB&model=240-D-002&category=All&part=Power+Antenna