Yeah the 3.5 is just as good as the 617...
Notice the people who have bent over and wrote a $13k check to replace one don't say things like that!
I wouldn't touch a diesel W140 unless it was mint and I got it cheap, the gas engines are so much better then the 3.5 and cheaper to buy also. When I was looking for at W140's 1999 S320's seem to be a real bargin.