LSJ longblock + MS2 or Fast XFI,BS3 etc. The standalone engine managment will set you free! Dont pigeonhole yourself into a factory ecm unless you HAVE to. You'll thank me later. (when you tuning on the fly-hassle free!)
A prepped LSJ with a bigger blower or screwblower can really put it down. The same with the right size turbo can be downright dangerous...