I looked over the block, head, and new head gasket and figured the head gasket wasn't correct for my engine because it blocked off a hole near the fwd end, so I drilled a hole there in the head gasket. Engine fired right up but after 5 min idling I saw the temp gage going off scale. I finally figured those were casting core cavities and the gasket was supposed to block them off. At least everything was still clean so I was able to lift the head w/ manifolds installed and swap in a new head gasket (w/ slight cleaning) and no more issues..
