Make sure you have removed 17 head bolts per side....ugh...I see gmc684x4 beat me to it...
I have seen experienced techs forget the end bolt under each end of the valve cover !
You can get a sharpened hook tool into the cup in the top of the lifter and use a slide hammer to extract....
Try spraying brake clean around the lifter body and let it soak a while....
The lifters on a small block will usually not come up high enough to remove the cam...if they are carboned up badly...
