Soak the cylinders with Kroil. It's better than PB Blaster at freeing up rusted pistons.
www.kanolabs.comAlso, have somebody hold pressure with a pry bar on the flywheel teeth while you use a wood block close to the size of the piston and a sledgehammer to smack the pistons a few times. Shocking the pistons helps break them loose.
The front plate behind the timing gears will make it very difficult to remove the crankshaft with the pistons still in place.
Jerry