Check your lifters before buttoning it back up. I just changed a head on my 6.2 and apparently one of the little wire clips that holds the lifter together was gone so when I pulled the pushrod out, the little dish in the top of the lifter fell out. Didn't notice the problem until I started it up and the pushrod rammed itself through the lifter. Luckily I was able to use parts from a spare gm 350 gasser lifter that I had laying around to repair the 6.2 lifter. Just something to watch out for.