installing high performance heads and cams on 01 silverado 5.3?

ok i have a 01 silverado with the 5.3 and i wanted to change the heads and cams to high performance ones.and i wanted to know if i buy the heads and the cams together will they come with the valve springs and pushrods.do i have to put better pistons to or can i leave the stock pistons.what else do i have to install besides the pushrods and the valve springs