An update:
First, thanks to all to weighed in encouraging me to be patient. I did follow that advice and spent three weeks working the head up and down with the puller, adding penetrating oil, letting it do its job, using wood wedges, and prying from the corners, etc., and it finally let loose and I got it off undamaged. Here's what I found:
The head gasket was not blown. I took the head to the head shop and it had two cracks, both around the No. 5 stud hole, one from the stud to the first water passage, then from there to the large water hole. The head was also slightly warped.The block, which was rebuilt many years ago, looked to be in great shape, and after cleaning I see no visible cracks, definitely none between the cylinders. None of the pistons showed water exposure.
I was taking the head off in the first place because of water on the dipstick. I also have now taken the valve cover off and found significant amounts of white gunk (which I have cleaned out). I have a prepared head I'm ready to put on, but I am concerned that I may not have found or corrected was what causing the water problem in the first place. Any thoughts on that would be greatly appreciated. And thanks for everyone's help!