valve clearance on 03 4.8

i got a 03 Sierra with the 4.8L and i'm looking at cams but i need to know hat the valve clearance is so i don't go to big and smack a valve. right now it's all stock exept custom dynomax exhaust.

also what would be a good cam to use. it's pretty much going to be my race vehicle. but i need a little street use out of it.