607 bhp may mean at the crank, in which case its pretty straightforward to get to that kind of power. 607 RWHP can be done with heads, rockers, cam, TB's and exhaust with a careful tune. John H built some great cars and totally ***** others, I would bet that if he knew it was for someone famous where scrutiny would be involved, he'd've done this one right. He probably screwed the next guy through the door.....the guy who only had money and not alot of fame!