I have recently conquered this problem. Like you, I bought a new (not a rebuilt/remanufactured) R-4 compressor. Like you, the part I recieved was from Murray, which I believe is a Four Seasons subsidiary. Like you, I could not make the compressor seal with the parts at hand. I ended up looking at the Worldpac catalog for the "hose manifold seal kit"; you can see it in Fastlane
here.
I ended getting the brass/yellow seal 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.