The diesels and the gas both have their place. The diesel is a great daily driver, good mileage, solid and safe car. The big gas cars are so much fun to drive. My 500 with the Euro engine can easily hold it's own against most cars on the road but at the same time cruise like a lemo. Only car I can drive for 6 or 7 hours, only stopping for fuel and food and not be tired. I just got the 560 so we will see how it does. The plan to remove the engine to replace ALL the chain guides and chain turned into rebuilding the heads, replacing all the rubber seals, guides and chain, oil pump guide and chain, trans rebuild (not me), replacing the differential and drive axles from a low mileage 420 (120K). So far my parts bill is around $700 not including the trans which I expect to be about $500 or less (good friend). Its strange how a simple job can grow into life long project.
Good luck on the engine swap.

__________________
84 500 SEL (307,xxx miles)