AJ, you need to do SOME research before pulling a number out of your ass and expecting to get that type of power from just shaving the heads.
To make that kind of power you need a combination of parts as stated above. Pistons are needed to net the type of compression you want in combination with shaving the heads....also different thickness head gaskets. You'd have to have work done to the heads so they flow better (port and polish), bigger valves, etc... and also the type of cam.
Just for reference, my mopar 360 has flat top pistons, I'm somewhere around 10:1 compression, heads are port and polished, and i have a mild cam.... I'm NOWHERE near 450hp. I'd be lucky to have 300hp at the crank.
Also what engine is this? Please tell me its not the 305.....
Oh and if you shave the heads to much, you'll have to get your intake shaved down as well, otherwise it will not fit.