You're in luck, the ECOTEC has lots of factory support and a better overall design than the LD9 and can support more horsepower with more stock parts than the LD9.
http://www.gmgoodwrench.com/gmgoodwrenchjs...9284§ion=pp
There's what they have to offer so far, and should be plenty to make a 300+HP streetable engine (with some forced induction, of course)