I want to have 400-500 rwhp (supercharged) what do i have to do to the bottom end and how many pounds of boost should i be at?

 

Well if I were you I would get a forged crank, rods & pistons (the crank probably isn't necessary but I say build it right the first time...). Also, a healthy blower cam grind and aftermarket heads would make it a lot easier to get to the numbers you're looking for. TFS and Edelbrock both make LT1 castings that should have the exhaust flow to give you a good setup. Oh and BTW, you might as well go 383 if you're going to invest in forged components. It probably sounds expensive, but if you want to go over 6 lbs and not use 100+ octane gas you're going to have to tear the engine down anyway, and while you're there you might as well spend the money so you get the most potential out of your blown combo and good reliability at the same time. You might also want to check out the forced induction section for ideas and/or ask questions there too. They'd be able to give you more specifics based on what you're looking for. But yeah, a blown 383 built right should be able to propel you into the tens once you get the rest of the drivetrain sorted out.

 

450 - 500 rwhp is very obtainable with a modest port to the stock heads if your budget doesn't include $2,500 - $3,500 for heads. You can run 9 - 10 lbs of boost with an intercooler and make safe HP while running 91 octane gas; drop your compression ration down to the 8.5 - 9.5 range. Post in the Forced Induction section.

 

ATI Procharger ! If you build the bottom end right you could run their stage 2 . I believe it is the one with the twin hi-flow intercooler. Like what was said earlier, bring your compression down to 8.5- 9.0 and get that blower grind. Heads will definately need work to realize full potential, so if money permits some nice cnc comp ported heads from AFR would do you right