It's really easy to get that kind of power from a supercharged 3800.

Xp or s1x cam
Double roller
130# springs
Milled retainers
Viton valve seals
E85
60lb injectors
255lph pump
2.8 pulley

That will put you in the 330-350 whp range through an automatic. With a manual, you can probably get to 300whp just by switching to e85 and skipping the cam.