I dont think you'd find a c. c. on your model, Merv. Its optional in the Japanese version. Not Singaporean and Malaysian, i.e. Asia-Pacific version.
As to the idle control relay, it is located in the middle of the 300se firewall - red coloured. Sometimes its called an overload relay.
For 280SEL, is your fuel injection KE version or L-Electronic version.
If KE - it should be the same place. If its L-tronice, its likely they dont come with it.
Let me know?