One could really go either way about this if one is going to mod this thing up to infinity. I'll get one question out of the way... yes the chassis are identical. As of now it is easier to get lots of horsepower out of the 2.4 block, since it has been around longer and already has an ecu crack. However I hear story after story about how tough/well designed the 2 liter block is. And if you where to look up info on the Red Bull drift racer you'll find that they started with a GXP and tuned it to hell and were able to achieve 500 horses, to which i believe they did only in order to keep it drivable.

Heres an article with some info on that racer http://www.conceptcarz.com/vehicle/z11543/default.aspx

and heres some specs http://www.solsticeforum.com/forum/a...5&d=1146232625

and heated discussions! Red Bull Solstice GXP (550hp) for Drifting Competition

Other than that I really would not know what to recommend, I'm a firm believer in "no replacement for displacement" but if there where ever a block made out of diamond and was only 1 liter, id probably go with that :P