What turbo are you going to use? What intercooler setup?
450hp ain't going to be a cheap job and if your going about it by trying to use 2nd hand let pistons your going the wrong way IMO...it needs built with the right stuff and the pectel is a good start. Don't forget cams and valve springs too.

Get your engine out n stripped to see what you have?
Have you had it on the rollers yet to see what it's doing?