Probably is a tapered shaft that was driven on. A lot of old Wilson irons had hosels, that when the shaft was driven on, the tip would kind of flare. This definitely can make them harder to get off. After heating, using the ram rod and Rlafoone suggested can work. Basically you’re driving the head off from inside the hosel. Another thing you can do is cut the shaft off enough that you can put the remainder club in the freezer. After a few hours, take it and then heat it. This process of temperature change can make the shaft easier to get out because the shaft material and head material react differently to the extremes in temperature (contracting and expanding).