Soaked nuts with PB-Blaster for 24 hours. Still had to chisel two head nuts. Two others came off using a 14mm 6pt scocket, the 9/16 just wouldn't hold. While loosing the head one of the cylinders wanted to come along with the head. I found a little c-clamp would provide enough resistance to keep it in place.
This core has the 95hp heads but 4 of the cylinders look like keepers.