This past winter I was replacing my head gaskets and was also having a tough time freeing the heads from the cylinders, until I tried a suggestion from Ken W. of VanAgain. He suggested that I tap the cylinder ears with a brass drifter and it worked! I used an 8" x 1/2" brass drift and tapped both opposing ears on the cylinders from side to side. This will cause the barrel to turn a little to each side and free itself from the head. It worked like a charm!
Good luck with your project!
Bob A
'86 GL
Massachusetts