The 5.7 computer will work as a starting point but a custom dyno tune from a local shop (if you can find one) woiuld be necessary for the correct prom. You can get a mail-order tune from someone like TBIChips.com or Wester's Garage, but you can expect to be mailing chips back and forth until it's dialed in. A third option, the one preferred by self-tuners, is the ebl flash program from Dynamic EFI which allows quick adjustments via your laptop without swapping proms. Expect a steep learning curve with self-tuning, I've been reading about it for a long time and it's a whole other language to learn.
The bbc tb will work but the plug from the wiring harness to the ecm is different and needs to be modified. The stock throttle body can be bored to 46mm, and with the right intake, will flow well enough to feed a mid-level 383 but if you're serious about 450 hp you'll need the 50mm bb unit.
You'll also have to get some 454 injectors (17084304) and a fuel pump that can provide enough fuel. Check out SPR Performance for tbi parts, good guy to deal with.
If I were shooting for big hp numbers like you, I would be looking at tpi instead of tbi, but I don't know enough about it to make any suggestions.
