Why do you want 450 hp? Where did you get that number? How do you know that's the amount you want? Is that measured at the wheels or the crank?
Once you answer those questions, I'll tell you that the physical laws that govern things in this universe predict that 450 hp from a 3.2L at less than 10k RPM on straight pump gas (i.e. no nitrous) will require 120% or better volumetric efficiency, which is just not going to happen without forced induction (i.e. turbo or supercharger).
If you intend to keep the engine NA and make that power, be prepared to spend $15k+ on valvetrain components, intake and exhaust tuning, custom accessories, and tons and tons of fabrication. It's just not possible on an engine that's anywhere near stock.
As far as I know, the power/torque record for a normally-aspirated SHO engine in a SHO body is held by Ernie Groce, and I
think it's 318 hp/279 lbft., and he's spent a LOT of time and money to get there. See his thread here:
http://www.shoforum.com/showthread.php?t=65753
That said, if you want to make high power (300+ hp) from a 3.2L, do yourself a favor and turbo it. It's the cheapest easy, reliable way to do it. Nitrous will get you there too, but you'll be blowing things up and spending a lot on refills before you get anywhere near 450 hp.
Don't expect to walk in off the street with no experience on these engines and make that kind of power right away either. There will be a lot of lessons to learn before you get there. Lack of traction, third gear, and halfshafts will all be your mortal enemies too.
Good luck!
