[rotorwrench]

I'd have to agree with Mart. The condition warrants work that is much better and easier done out of the car. As was mentioned, an engine stand adapter that connects the the exhaust ports is much better than worrying about cracking the rear bell area. The casting is not all that thick on the rear end there.

The one rusty piston is likely the sticking point. Just getting the valves out is a big job and they should come out to insure serviceability. If the engine was not so internally fowled and the cylinders were all still void of corrosion, things would be different. That one is just beyond that state. Everything needs to be cleaned & checked.