I second the supercharger. And as far as his block goes, im sure its pretty strong. My 2.4Z can hold up to 500hp

 

I don't know about stock internals on a 3.8 (gen 2) holding up to 500hp.. I would say 300hp.

The supercharger is going to be an expensive route, but at least the fuel curve is linear to stock so it won't be so bad. Turbos are a lot cheaper and add bigger HP, I'm sure there is enough support out there for turboing that motor, it is one of the most popular v6s in the world.