Mercedes would sell you a five speed but the manual trans mercs are such awful cars to drive that they ended up with large stocks of Five speeds trans. I know someone who has a w107 350SL with a five speed. the trans was cheaper to buy from mercedes than it was going to cost to rebuild his 4 speed. The biggest advantage was that the fuel mileage was improved to the point where he even beat diesels in economy trials with the local mercedes Club. So,you could have a five speed in any car you wanted you just had to order it. (option #428)