we use these heads in our street stock class{dirt racing} We have a .488 lift rule and i know we have guys using stock heads and valve with just different springs. get your self a good set of poly locks and if you set them right you should be fine

 

the heads have been accomidated for higher lift (machining and springs) they also have undercut intake and exhaust valves. the exhaust valves are also larger and the heads are ported. Im running the crane cam gold race 1.6 roller rocker so they came with the poly locks already and that is what im running