500 Hp Slant 6

I've heard of a naturally aspirated six getting 1hp per cubic inch plus with a long run ram manifold. Here's a link to the article.
http://www.moparmusclemagazine.com/...1962_plymouth_valiant_slant_six/photo_01.html

There's also an article on fuel injecting a slant six on slantsix.org, but that recycles components (electronic control unit, mostly) from a GM V6 that has the same displacement. So it probably won't have nearly enough performance.

Keep us all posted, I love the idea of a high performance modernized slant six in a lightweight early A body.