There was a site,  http://www.560sec.com/   but its owner wants to sell
it so the content has been suspended.

try: www.mbz.org and look through that site or the M-B Club of America

Go to mbcoupes.com.

Steve;
Hope you are handy with tools. also, make sure it is the US version VS
European version. In those years there were a lot more differences between
the two than there are nowadays. Wiring diagrams and some parts may become
hard to come by.

Good luck.

Monterey