I have an 84' 300Sd. On the rear of the Ac compressor where the refrigerant lines bolt on there are two o-rings and two metel o rings. the system was flat and there was a bit of oil stain/wetness from the suction line side. I removed the lines and found only one nipple sticking out from the forward side of the line assy. it was on the liquid side and as i removed them the other metal o-ring fell out. is this right or is something missing?

Do a search for "stepped port" compressor seal. You'll find some good info with pics regarding the proper arrangement.

yes, what you found is normal for a standard replacement compressor.
you will need to get replacement steel spacers. were yours both bare metal colored with black rubber material in the center? that would be equal spacers.

So you use the steel spacers with the recessed o-ring, seems like a flimsy set up. Thanks Whiskydan I found the other posts!