Well, the benzbin.com lists the Behr stock unit as 80 degrees C. If you want to verify this, please call Mercedes at 18002220100 and press 7 for tech, mon through fri 9-5 EST. Have your VIN ready. You may have to also call a local dealer.
From the site:
80 degree Thermostat Kit
G4001-15462 Behr List $35.00 30.80