I finally got around to removing the manifold today. The PB Blaster that I sprayed on the nuts worked well. I gently torqued them off with no problem. I was prepared to use heat and worst case dremmel cut the nuts off and if needed replace the studs. Only 4 held the manifold off. As I removed tension on the aft nut I started to smell the distinct odor of antifreeze. That worried me. Before I could get it completely out the manifold came off due to the rust; see pics. When I removed the stud with the bolt the anti freeze came gushing out the hole.
I put the stud back in to evaluate and save the whales from being poisoned by so much toxic waste being vented into our environment .

I was not aware that the stud holes penetrate all the way into the water jacket. Can anyone confirm that is acceptable convention? The block is not cracked and I see no damage.
For now I am cleaning things up. being careful not to get crud into the intake openings. I suspect I can blow those out through the spark hole one at a time by advancing the fly wheel until all are clean??
One barnacle and fungus growth successfully removed!
Details of the old repair job. I am lucky no crud has been sucked into the cylinder as far as I know. That would be catastrophic!