Don't forget the W140 outside chassis changed a bit. Added more lines to the body (trim, changed rear end look). I've a M104.990 engine, 1993 Benz 300SE and am satisfied by its power. Had to track down a vacuum leak that was robbing it of acceleration, but found the culprit in a hardened breather hose that was letting the engine suck in outside air from the underneath. Have had problems w/ the 722.5 trans. (reverse failing & then forward gears - had to be rebuilt) & the well known cylinder head gasket defect on the I6, as well as the wiring harness failure & Bose amp problem as well as closing assist & lower control arm vibration but all in all, I like the older chassis look compared w/ the new look. Am told also that the older I6 had a bit more power than the S320 later version & some better quality materials here & there, but am not certain. Someone said it had to do w/ the catalytic converter add-ons which lowered the horsepower compared w/ older models.

Once you get to know your car, these problems become more manageable if you really love your car as a hobby. Just my 2 cents . . .