I'm assuming you're not looking for a full bottom end rebuild (??). 450 ponies from an 8.5:1 383 is a tall order. But here's some tips on getting the most out of it: I'd first focus on getting the compression up.
-Make sure you're running .020 head gaskets.
-Closed chamber heads are a must on a 383; Eddy RPM's or Source Stealths. 516 castings with oversize valves and an MP-template port job will work, but once you spend the money to have that work done, you're most likely within a McDonalds lunch of a set of stealths.
-Short stroke, low compression motor, so too much cam duration will kill your bottom end, Something in the range of a Comp XE275HL grind would be my choice.
-A 383 will be a high RPM motor, so bigger carb than you might think. I have a 750 on mine, and it works well.
- 1-3/4" headers are fine for a 383.
- Gears, Gears, Gears.... 3.91's for a street ride.
- I like the RPM manifold for a street car, but a single plane will work well, and maybe make a little more top end.

Tuned right, that outline should get you around 400 ponies, and will allow you to hold your own on the street.