Sorry to resurrect a thread from two years ago, but since I couldn't find definitive answers when I was searching, I wanted to post my results.
I have recently conquered this problem. I replaced a bad compressor with a new R-4 that had stepped ports. My old compressor had even ports with internal o-rings, and you simply bolted the hose up to it. Not so here. My compressor came with a thick green seal and a couple of thinner red seals. The instructions laid out a number of combination, none of which matched the set up in the Mercedes. I ended up looking at the Worldpac catalog for the "hose manifold seal kit"; you can see it in Fastlane
here.
I got the brass/yellow seal seen in the kit from NAPA, its simply referred to as a "thick yellow seal" for the GM R-4. They had to order it, cost around 4 bucks. It is wide enough that it covers the deeper port, while the green one mates up on the other side. If you are under the car looking at the compressor, and your feet are sticking out the front end of the car, the green seal (with the short pilot) will be on the left side, and the yellow/brass seal will be on the right. Once this was taken care of, everything snugged right up.