The new Hemi is pretty huge externally. LS needs way less room and performs very well. A friend of mine bought a LS3 carburated crate, bolted it in to his street '68 Firebird and run 11.3's. Slightly cleaned the heads, a new cam and it runs 10.8's all day long. The brand new all aluminum engine cost less than 6000$. The heads flowed 323/215 cfm at 0.6". I have not played much with the new Hemis, but most of the parts are way more expensive and harder to find. They do have potential too, but if fitment and cost is your main problem it's easy to understand the LS route. And yes, we do have a 3 gen Hemi, although it's in a Jaguar. http://www.youtube.com/watch?v=7ZA4euk6R0U