I have the same scenario on my 1995 SL500. Same speed too. New tires, balanced, new wheel bearings, brand new drive shaft, new brakes and rotors, new front struts and new motor/transmission mounts. Still have the issue. I find that the vibration is there when the tires are cold. Tires are Michelin Pilots. Once the tires heat up the vibration goes away. I live in Florida so the tires heat up pretty quick. It's definetly annoying but unless I'm missing something and I might be, we'll have to live with it.