If it's an auto the stock 4L60e will cry and will grenade with power, they are weak unless otherwise built. 6 speed manual will hold good power to a point aswell.
The fast intake isn't a worth while upgrade. Think about the dollar per horsepower here. $950 plus a throttle body for very minimal gains. You'd see far better power increase with just a head swap and cost way way less. LS6 intake should be good for well over 400-450whp and you'd need some pretty aggressive camshaft and what not to see that. I see it too many times over that people just waste their money because it's what someone else did and they wish to follow.
Swap the factory diff for a eaton posi/tru trac and let it eat. A 9in swap is pretty overkill for what you are after. Tons of turbo truck guys run their 10 bolt to 600+ whp.
