for the 300td, an OEM 'euro hitch' was the Oris E115-4.
i've got one on my euro wagon.
there's a PDF showing the hitch and its mounting/install
here.
Capacities (In English) :::
permissible total weight: 2,400 kilograms = 5,291pounds
permissible "supporter branch": 1,900 kilograms = 4,188 pounds
permissible trailer hitch tongue load: 75 kilogram = 165 pounds
note***this is NOT the same hitch that came on W123 sedans (which have a lower capacity cause they ain't got no badass SLS
hope this helps.