Locked Engine

Most likely the rings are corroded in the piston lands, so the pistons are toast. Take the heads off, soak the bores with any of the goop stated above. Take a breaker bar with crank bolt socket and while someone is standing on that, another dude is beating on a 4X4 wooden block on top of the pistons ( one at a time) until they all start to move. Then remove all pistons for inspection. Hone the cylinders to clean up and if they do,install the new pistons, rings and bearings.

Good luck!