I have a problem with understanding why someone needs a 650 hp motor that is only going to be street driven and never raced and wants to be reliable???? That is a lot of strain on parts to make that much power to be pounded on at low speeds for bragging rights. lie!!! and leave it stock. That's my .02. Don't get me wrong I like a lot of hp but i use it for what intended.
Come on now, when people or some government agency try to tell me I don't need more than 650 or 700 hp in my car. I won't hang out with them anymore. Who needs that kind of negativity in their lives.
Modern aluminum heads, quality stroker bottom ends and good valve train choices make 650-700 hp seem pretty mild compared to what race engines put out at similar displacements.
Computer engine management, injection and turbo/blowers make 900+ hp reliable and reasonably tame when not building boost.
Look at Hellcats, Demons and the new Corvettes. Heck, I'm helping a buddy put together a 940 hp blown LSX in a 67 Chevelle with a 6 speed and a full Art Morrison Chassis. That should just be about right power to weight ratio for the street.