lightest NA engine capable of making 400hp

If you want an engine that is capable of 400 hp but without forced induction, what engine platform is the lightest? exclude exotics like Ferrari or even Porsche.

The obvious answer might be an LS, but there are lighter engines out there.

The Audi 4.2l gets there but I think it weighs about the same as an LS.

The Rover 4.6l with a stroker kit (5.0l) is a possibility. there is aftermarket availability but not cheap.

the AL version of the man o'war 302 block is a possible candidate. the block costs a lot but the 302 aftermarket is low cost.

how about the Nissan VQs...can they make that much NA power?

are there any other v6's that can get there? I'm guessing any straight 6 that can make 400 NA hp is going to be really heavy. what other engines am I missing?

found an article showing an NA VQ can make 400 up at the crank
http://www.superstreetonline.com/how-to/engine/modp-1303-nissan-350z-vq35de-engine-build/