I suggest that you remove the valve covers and inspect for obvious, stuck valve-train to eliminate valve-train damage,(from corrosion after sitting so long). I have seen a stuck valve stop a motor from turning over before. Force, will result in bent valve-train for sure if a valve is stuck in it's guide or on its face. After that I would remove the injectors and try to turn it over with little force. Next, I would remove the oil pan an inspect each piston to cylinder wall for a stuck piston (just try to wiggle them, you'll feel them move if there free. Then check the rod to crank for the same wiggle. And lastly try the crank for wigglage! With this process you can quite easily get a good overview of your whole engine and find the problem that is holding the engine stuck now. The one thing you won't see or feel is the camshaft, It's my experience that it wont be stuck. AS for soaking the cylinders, CLR house hold cleaner will dissolve rust and Coke will work quite well. Also hot transmission fluid with 1/2 kerosene works ok.(Not quite boiling! the thermal shock helps) Be careful and don't use too much force!