From what I read before [not claiming any experience], the C5R 427 is a great N/A engine for road racing, but the LSX or World engine has more tolerance and stronger walls for boost. I think LSX is more reliable in long run that LS7.
As far as turbo goes, the engine bay seems too small for all those tubes and stuff. Techo makes a nice addition to that LSX.
I've been thinking of the same thing except with less power, by swapping the LS3 engine with a LS9 from GM. What I like to know, what do I do with my brand new LS3 engine? Do I sell it? How much will I get for it?
[update] This article is a good article on LSX and it's comparison to C5-R:
http://www.vetteweb.com/tech/vemp_08...ine/index.html