I've not done this myself, I was just repeating what I've heard. I was told, the best place to get the pump bracket is from a W210 (dual oval light) E320 at the junk yard... but, do note, taking all those pumps off and reinstalling them is a major job.
I have a 1994 E320 station wagon. I am in the process of replacing the older belt tensioner with the adjustable rod to a automatic tensioner without the need for the damper and the adjustable rod. According to the forum in your words, "there's two styles of tensioners and people have been known to retrofit the newer style on an older engine (the new style started in 1995). the old style has the threaded rod to adjust the tension, and seperate damper, the new style does away with all that, and is just spring loaded. you can't simply swap them, you have to swap the bracket that they are mounted on, which is also the bracket for the power steering and water pumps." I would like to make the switch or retrofit from the old belt tensioner to the automatic tensioner as describe above. Exactly what parts do I need to make it work?(automatic tensioner part number, replace water pump brackets, exactly what kind of brackets and where to get them?) My engine serial number is 104 992 12 061 339.