W126/M103 motor mounts (Mike Murrell)
Mike and anyone who's interested,
I set out to replace the motor mounts on my 91 300SE. If you have the patience to lie under your car and twist a 6mm allen key 30-degrees about a thousand times, replacing the motor mounts on this chassis engine combination is quite easy. Forget how restricted access looks from the top. You can do this job without opening the hood. I mean you should have it open to make sure you don't break anything as you lift the engine, but you don't have to turn any wrenches from above.
The heat shield on the US passenger side got in the way of the inner allen head screw, but all it took was releasing the big bolt and lifting the engine a little to loosen the heat shield.
It turns out my motor mounts are either new or amazingly fresh for having 140K miles. The car is 14 months and 11K miles new to me. They were almost as clean and definitely as stiff as the replacements. It might be some strange kind of rubber that breaks from the inside, but again, they look and feel like new.
I haven't checked the rear mount (kids came home), but it looks as simple as the set up on the W116/M117 tranny mount I did, which is a trivial task.