First thing, exactly what do you expect from the car? Is it just to look super cool or will this be for race purposes?
Big one, what is your budget? The full Motec race dash and ECU is likely going to be in the $10k range when all is said and done.
I'll assume your going full standalone on the motor and not relying on the stock LSx pcm. Given that, what further dataloging do you need beyond what the PCM provides (be it BS3, AEM, etc.)
For gauges I really like the nexus setup, plus they look flippin sweet. And have the "idiot lights" built in, being that they will change color if they go beyond a given paramater. Expensive, and rather limited selection, but very nice setup.