Trying to free a stuck engine

You better run a bore scope into the cylinders first. If one or two had water sitting in them you are wasting your time. Otherwise, I recommend the 50/50 Acetone ATF mixture. I only had one engine unstick from the soaking approach. That was a 273 that had dripped a bunch of stale gas out of the carb over time and had varnished the rings to the cylinders.