If it hasn't moved after some time of soaking the cylinders with oil, it's probably time to pull the cylinder head. Don't waste time turning on the vibration damper- - - -you can't develop enough leverage. Take the sheet metal cover off the bottom of the flywheel and use the chisel-shaped end of a shepherd's crook wrecking bar in the flywheel ring gear teeth, braced against the edge of the bellhousing. You can put several hundred ft./lbs. of torque on the crankshaft that way. Just don't get rowdy and break teeth off the flywheel. If the engine moves a little, back up and turn it the other way a few teeth. Keep that up until you can get full turns.

If it's necessary to remove the cylinder head, figure out which piston is moving down, and massage it with a block of hardwood and a BFH while someone alse pries on the flywheel. When that one reaches the bottom, find another one on the way down and do it again. If it's really stuck tight, chances are the cylinders will be rust-pitted badly enough to require a rebore and bigger pistons. Good luck!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!