I have a set of valve springs and retainers for sale that i was told are crane cam springs. These springs will drop into a vortec head without any modification and allow for .550 lift without having to modify the seats, guides, or seals they just drop in. These where originally installed on a vortec head and where tested by a machine shop to make sure they really would support that lift without any modification. I was going to use these but i couldn't because i have self aligining roller rockers. In order for these to work you have to have either the stock rockers or roller rockers with guide plates. This is a pretty cheap way to allow for more lift. These valve springs and retainers usually go for 150, im asking 100 OBO