This has been mentioned in the FS2004 Forums. But just in case you never visit that forum, here's an announcement.
I have finished a Beta version of the 1998 Mercedes-Benz SL600. The Full package will be released later on with all the feature intended.
I uploaded the Beta version yesterday in simviation. It is now post on the website's main page under "FS2004 Misc".
You can post your opinions here if you like.