Here's the story so far --- as you all have found out, the easy things in life are usually a real pain.
Ordered the viscous clutch (part number x) from FastLane ... delivered quickly with personal attention from Phil. Part number on box is x but part number on part is y. Called Phil who, again, was very responsive, and he overnighted me another one. Same story - part number on box was x (correct part number per CD-ROM) and part number on part was y.
Agent from worldpac (owners of Fastlane?) got on the email chain and pointed out that part number x had been replaced by part number z which required additional parts. The story is getting more interesting now, huh? I removed old clutch using a 3/8 drive with allen head that I "modified" with a grinder in order to have enought clearance (can just barely slip your arm between fan assembly and the radiator on 350 SDL. Old clutch looked OK, but was a bit loose. Unbolted clutch from fan assembly (3-10mm bolts) and bolted on part number y ... fits fine with bolt holes lining up, but a bit smaller diameter of the main clutch body. Tried it - seems to run a bit warmer ... about 5 degrees or so. However ... yep, a bit less wobble, but still not stable ... grab the fan again (turned off) ... convinced now it is the coolant pump shaft bearing ... have ordered same from FastLane (cheapest one they show in catalog).
While picking up a couple of gallons of the world's most expensive and special coolant at the dealer I asked about what they show for replacement for the clutch ... the answer is "old part number crosses to the new part, but it also requires a new fan blade assembly." I guess the new clutch is different somehow ... since the price of the clutch with blades at dealer was over $400 and the clutch from FastLane was $160, I guess I can afford to live with the "not kwite write" clutch.
If this one lasts 100K I am OK with it ...
I like electric fan idea more and more ...
Hope this story helps someone.
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg