I hadn't been keeping this thread current, although the car is almost done. I made a deal with another mercedesshop member (who happened to have been interested in the same parts car that I was looking at) to tow the car to his shop and then have me take just the parts I needed. He probably still has the transmission, but I can't speak for his interest in selling it, I think he was wanting to keep parts on hand for future projects of his own. You can contact him through the forum as "autozen".
I'm going to post a wrapup when my 300 is back on the road.