Well..to start...
If you want that kind of N/A HP, start looking at the TFS heads. Your not going to get anywhere near 400WHP from PI's, even once they are hocked way out.
Second, you'll need cam's. Before you choose, please decide on if your going turbo or blower (If blower, which style ie. TS, Centri, etc). You cant have cam's are great N/A that work well for Boosted apps, and turbo cams are different than blower (s/c) cams etc. So try to plan out a little.
Third, Once you get to desired N/A HP, hate to be the bearer of bad news but you wont be able to run much boost unless you got the giant chanbered TFS heads, then you would still be running a high 9 CR. Boost + high CR on stock shortblock = no bueno. Just warning.
Might be a good idea just to get some hitech cams and PI heads/intake as mentioned above, then start building an engine if you want to go crazy with a blower etc.
NOW PLEASE READ: This is not to say you cant run low-ish boost on a PI swapped NPI shortblock, but anything around/over ~450hp will be in connecting rod snapping territory. Just be careful, and try to plan out as much as you can.