I forgot to mention that that aluminum engine was the 215 ci V8 that GM produced in two versions from 1961 through 1963... I have one in my garage, waiting for some worthy project. They were great little engines, the 1963 Olds engine produced 200 hp at 10,500 rpm stock from the factory, with no turbo, just the 4bbl engine. (That's the one I have.) It only weighs 275 lbs without the exhaust headers. The buick version had different heads and intake manifold, but was basically the same engine. In 1964 Buick came out with a 300CI cast iron block with aluminum heads - if you can find the 1964 heads and install them on a 1963 aluminum block you have a real good starting point for lots of power, as the 1964 heads had much larger valves. With a bit of work, you can also put the 1964 crank in the 1963 engine for a stroker engine. These were very popular with the sand drag folks. GM sold the castings to Rover, and when the gas crunch hit they tried to buy them back, but Rover wouldn't sell... They have added more ci to the engine, and also added fuel injection, but it's still the same basic engine.
Sorry to get off the Mercedes track, but I thought I'd try to clear up the confusion.... The Buick I think people have talked about is indeed the 3.8 V6, it's a fine engine also.
Etc... - see previous post