1977 ford 3600 trouble starting

[Baby]

Tractor was left out in the weather for about 4 years with cover over exhaust. This is a diesel tractor and I believe it may be seized up.
I was told by a friend to jack up the rear end, put it in high range and high gear and try to push or move a rear tire. Tractor is loaded up on a tall gooseneck trailer with a bush hog attached.
Any help would be appreciated....thanks...

[DanD78]

I think I would remove the valve cover and make sure there are no stuck valves before trying to turn the engine over. Jacking up a and trying to jerk a wheel will work but I would rather put a breaker bar on the nut on the end of the crank shaft and pull it over that way. If you can bar it over two turns by hand I would hit it with the starter. You may also want to change all the filters and put fresh fuel in as well.

[Ultradog MN]

Pull the injectors and pour half a cup of Marvel Mystery oil down each cylinder. Let it sit for a week.
Then put a battery in it and bump the starter a couple of times. Likely that will unstick her.
If it breaks free and turns over it'll spew MMO everywhere but that can be cleaned up.