David, I had the same problem on a 74 450SL. My problem was the ignition timing. It had slipped to 30 degrees retarded. It still ran but overheated. Also, The radiator core could be the wrong type. Other things to check. Wrong impeller clearance on aftermarket water pump use only OEM, Fan clutch, faulty or no aux fan, clogged AC condenser coil. I have also heard of a desert package that includes a bigger fan blade for hot weather driving. If your car has a tranny cooler in the radiator check the tranny to make sure it is not overheating.
Thats all I can think of now.

BTW the 107 is prone to overheating just for the fun of it.

Bill