I notice you reside on the east coast. If you are in the rustbelt and I suspect you are start with the cylinder soaks as mentioned. If you get any movement go back and forth very easily until you can turn one revolution. I think your initial soaking period before you get any movement might be quite a bit longer than two days though. The one thing in your favour in our poor outdoor storage climate is generally diesels take a longer time to initially seize up. I think the lesser clearances between the walls and pistons actually help. You want to soak for a period on about a month I think. Too good a chance of breaking or damaging something otherwise. Miracles never cease to amaze me though. It should not be loose now but might be still. I expect some of your valve stems might be rusted causing stuck open valves as well. First things first though.