Pull the valve cover and loosen or remove the rocker arm shaft. Remove the pushrods. This will solve the potential problem of stuck valves adding to the resistance of the engine to turning. Pull the spark plugs and add several ounces of a 50:50 mixture of acetone and ATF, or Kroil if you have any. After a few days, use the chisel-shaped end of a shepherd's crook wrecking bar between the flywheel teeth and the bellhousing, being careful not to break or damage any teeth. If the flywheel moves at all, alternate between moving it a few teeth in both directions. Patience!
Worst-case scenario, remove the cylinder head and use a chunk of hardwood such as oak or maple that will be a close fit in the cylinders, and smack the top of the pistons with a BFH to break them loose.
Jerry
