First get a tuner, something like a Diablo Predator or Trinity programmer. Ur gonna need it once you do the mods.
Besides that, I recommend a cam and some performance heads. About 2.7k total before installation. Try getting a hold of Stu over at Inertia Motorsports he can set you up with a great package and deal if you order all at once, it's where I just got mine from.
He'll probably recommend the spartan plus cam, which is not yet on their website, and from what he says will add about 45-50 to the rear. As for their performance heads when installed in conjunction with the cam, you will get anywhere from 75+ to rear.(Just my estimate)