Wiring should be there but with a funky MB only connector...at least that was the case with my old 1992 190E 2.6. I'm not sure about the older models though. Did you call a dealer? I suppose you can cut the wire and put your own connector for whatever speaker you put in. I do know that unless you put OEM in you'll be limited to what will drop in unless you customize the opening. If your going to rock the house then definitely go with some fat monster speaker wire throughout, but then, you must know that. Happy motoring.

Jim
1992 500E