The wagon attachments I spoke of also only bolt through sheet metal. Since there is no frame on these cars, nothing a hitch would mount to is very strong. I'm not sure why you think the normal hitch can't pull more than 1000 lbs. MB rates these vehicles for pulling up to 2500 lbs and lots of people here have pulled a lot more than 1000 lbs with the normal hitch. There's a picture on here somewhere of someone pulling a tandem trailer with a vehicle on it with a 126.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13