Post the cam specs, heads, and other mods when you get done, kamori, and we can try to help point you in the right direction.
I've read and heard pro and cons about using the 454 throttle bodies; seems their mounting flange is different than the 5.0/5.7L throttle body flange and can be a source of vacuum leaks, plus some people have had to have their intake bored to 2" to accomodate the larger 454 butterlies.
There are different schools of thought on making a modded TBI engine make power.
I myself went with the stock size 5.7L throttle body that came on my truck, and stock 61 lb/hour injectors, but I upped the fuel pressure with a fuel pump for a TPI Camaro.
I am looking to replace the stock injectors in the near future with either Caprice police car 9C1 injectors rated at 68 lb/hr, or injectors from a 454 equipped truck so I can lower my fuel pressure as it is causing some idle issues due to the high pressure.
Depending on how far you want to go with this project, you might find yourself needing a vacuum referenced adjustable fuel pressure regulator (VAFPR) to help lower the fuel pressure at idle and make tuning easier.
If you want to do your own tuning, visit
www.moates.net for just about ALL your tuning needs for your vehicle.
The software for datalogging and tuning is abundant, and a lot of it is free, it just takes time to get it right.
I've been tuning my truck lately with a wide band O2 sensor to try and get it as close to perfect as I can before I start really pushing the truck hard.
Let me know if I can be of any help. I have a lot of sites bookmarked that are all about tuning your computer controlled vehicle......just let me know.