how old is the head gasket, if it hasnt been changed in a REAL long time, it will stick to the block "like glue", the way i do is i leave the intake manifold on make sure ALL the bolts and brackets are off then push down and pull up on the mani, "wiggle it free" that way there will be no prying. everytime i have done it this way it was effective. and i have done this many many times.