Its a 1972 280seThe extra wide 18" wheels use approx 11mm ofset. The real question is will the tires rub on the front fenders and suspension components.
Which W108 do you refer?
Wheel size and offset are two different things. I have 16" wheels on my '72 280se 4.5. They were too large of an offset, so I used spacers from H&R. They fit fine in the wheelwells. Look at Cox Groups 111 chassis with 18" to see that anything is possible.