Due to the high gas prices i am pondering the idea of somehow fitting a turbodiesel engine into a 1972 300SEL. Does anyone know if this would work??? would the w116 turbodiesel engine fit?????

I don't know anything about the physical fit of it... but you think gas prices are high? Well the cost of an engine swap is MUCH higher. You'd probably have to drive close to half a million miles to just break even! NOT worth it.

David is right. The cost of switching the engine would more than eat up any savings a diesel might give you. Its alot more involved than just putting in a new engine. Your transmission might not mate to the new engine, the exhaust probably wouldn't mate right either, then there is new ignition, fuel delivery, engine controls, and on and on. Like david says, you'd probably have to drive for 15-20 years on the new engine to break even on the gas.