benz bought chrysler, not the other way 'round. and they promptly sold it, now it has fiat as a partner. but some of the best benz units were built before 1992.
stay away from the 3.5 litre. i have a '91 350SDL that blowed up the engine, and it was replaced with the 3.0 om603 from a 1987 model. pretty much the exact same engine, except the 3.5 was bored bigger for the extra displacement. as it turns out, this made the walls between the cylinders too thin which resulted in warping of the cylinder walls and the eventual catastrophic death of the engine. the 3.5 litre is known as the "rodbender" engine.
the other pitfall of these engines was the trap oxidizer. originally these were placed in such a way that when (not if) they failed it sent particulate into the turbocharger which results in catastrophic failure. benz had a factory fix for these by putting the trap oxidizer downstream of the turbo. best bet is to remove it entirely. otherwise, the om617 and om603 are nearly legendary in longevity and performance.
yes, although some 3.5's have gone the distance also. If the engine was replaced under warranty then they are supposedly bullet proof.
If not probably not a good used engine purchase unless just buying for the head which is an improvement over the original 3.0.
I am thinking of doing this swap also... currently 4x4labs has kits out for all GM stick shifts and the W56 yota transmission.
I keep going back and forward on this one