I've studied the cars long distance and have been on the fence about them.
www.heckflosse.nl/ I think is the website that will answer any questions. I think a '65 is a 200D.
I've gotten close to pulling the trigger on one of those, the looks are the coolest, the performance with an auto trans roughly equals that of a driveway slug (without salt) and I think the 4 spd is mandatory. I don't expect a lot of appreciation of that particular car, financially, and it's just a call if you'd like to drive one.
If you've got the room, you can't find a simpler car and they are great to look at. I've been told by Benz that the parts are readily available for eng. drivetrain, etc. 55 hp, I think, is the number for a 200D. Rust is always the deciding factor for me and is the reason I basically gave my 6.3 away.
I have a bunch of cars and have decided to stick with my 79 300SD for now to satisfy the diesel obsession, but it would be a cool car. Oh heck, buy it, if it doesn't work out, maybe I'll take it some day.
Let me know what you think of the website. Good Luck
Roger