Hello,
The next time you're car stereo shopping, mind the reference guide nearby.
Almost all shops (which carry auto stereo's) have guides showing which type stereo's and speakers fit, what model of vehicles...
Failing all else, you could simply e-mail the "veterans" division of Mercedes-Benz website and they should be able to respond to your question. (They are very helpful.)
(I'm assuming you do not still have the original books?)
Best of luck,
Mustapha