Lots of penetrating oil, lots of time, and quit twisting on the front of the crankshaft. If there's a bolt in the end of the crank you'll break it off or strip the threads using that much force. Take the sheet metal cover off the bottom of the bellhousing and use the chisel end of a shepherd's crook wrecking bar on the flywheel teeth. Turn the crankshaft until it gets tight, then back up and turn the other way. Keep going back and forth and eventually you'll get a complete turn. There's a good possibility there will be some permanent pits in the cylinder walls where the rings have rusted to them that will require reboring the engine and new pistons, but get it running if possible first and see how bad the compression loss and/or oil consumption is. You might get lucky.
Jerry
