Personally, I would go with a LS1 5.7L engine. It's a much cleaner setup. The intakes sits lower. Aluminum is soooooo much lighter and could be polished to show quality. The LS1 engine is very plentiful and easy to find. Performance parts are available most anywhere for the LS1. Horsepower to weight ratio is very good with the LS1. LS6 is quite a bit better if you can find one, they are easily acquired, also. 405 hp straight out of the box is quite respectable. Next option would be to start with an LS2. You can get 500 hp with a few bolt ons on either the LS2 or LS6, they both use the same heads. Just my two cents.