Like Cees, I got the first chance to use the gear-reduction starter in my car yesterday. Great improvement! It is higher pitched but quieter and spins the engine like a top. The one I'm using came from a recommendation from Jim Villers. They use them in the 190SL as well. It's from OBB and cost $102.50 plus shipping. It weighs 8 lbs. Part # is 16959N Here's a link:
http://www.obbstartersandalternators.com/starter-16956n-sr10x-p-1324.html?osCsid=e4554089d5fc6460cffb7b692716b7b4One of the holes is not threaded so you'll need a 12mm 1.75x80 bolt and nut. And it has a spade connector on one lead so you'll need a spade to ring adapter.