I think that the Subaru boxer engine is an excellent application. It has a high power density and low center of gravity. It's also very smooth and durable.

I'm digressing, though, into one of my favorite pasttimes, daydreaming. I'm wondering what else may fit into the back of an 818. I know it will never fit an LS7, but I know that there are probably some options other than the boxer. I imagine that the high mpg version will use a transverse mounted inline 4 cylinder, so I'm thinking it may be able to use all kinds of transverse mounted engines. I'm thinking a lightweight motorcycle engne like the one on the new Kawasaki ZX-14R.
http://www.autoblog.com/2011/10/11/k...stest-acceler/
They aren't saying what power it will have, but I'm guessing it will be well north of 200 hp. The engine and the gearbox combined would probably be a bit lighter then the boxer setup. The only catch is no reverse gear. That problem could be solved with a foot hole in the floorboards.

Anyone else have a crazy idea?