In all honesty, a rebuild with KB flat tops set to 0 deck, anda medium sized hydraulic cam (230ish duration at .050) will make 500hp or very close if it's done by a performance shop. It's not magic, nor expensive. No exotic heads, just a good performance 3 angle valve job, adn excellent machining gets you there.

Well, art is art, isn't it? Still, on the other hand, water is water! And east is east and west is west and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does. Now, uh... Now you tell me what you know.