This same thing happened to me and I ended up pulling the head and cylinders and
STILL had to beat on them quite awhile until I got the cylinders off! After pulling
the engine (something I really dreaded doing because of my inexperience) I was
glad  because I was able to do much more rebuilding (rings, bearings) than I
originally planned. Now I won't have to pull the whole thing next year and do the
same job over.
Actually, I was quite amazed at how easy it was to pull out the engine.

Good luck!

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