To those who might be interested...I replaced my old rubber shift knob off my '85 300CD-T with one off of a 2000 S-class I bought off of eBay (BTW for $35.00

). The procedure was as follows: Since the knob and shaft are all one piece on these models (and I believe most 80s MBs), the knob/shaft unit must be removed. After a fairly simple removal of the assembly, I cut (yep, cut) off the old rubber knob down to the shaft. Next, what appears to be a type of washer on the top of the shaft was broken off (by a rapid, repeating twisting action). And finally, I took the shaft to the grinding wheel and made the round shaft less round (I shaved off the sides being VERY careful to make them parallel so when the new shaft was put on it would be straight). This worked like a charm and its a nice snug fit because the new knobs use the same diameter shaft as the old ones.
Pretty simple, looks and feels great!
Garrick
'85 300CD-T
'86 420SEL (possibly for sale soon)
'94 Land Rover Discovery