James,
I have the same car. I had Jim Forgione supply me with a resistor device that clips right on to the temp sender. He has various models but I wanted something to turn on at 88C. It turns off at 83C. While my aux fans are on frequently my temp has never risen above 90C except on a trip to Parker last year. The air temp was 115F and I was driving at 80 mph. The car temp ran about 105C.
Something else I noticed is that a radiator out of my '95 E420 is a lot larger than our 300CE radiators and will fit in the same cut out. My E420 barely gets to 80C even in the hottest conditions.
Email me if you want to see my resistor installation.
Anziani