They're a close fit and get rusted on pretty good. I'd try soaking the fan's collar where it goes over the shaft with a good penetrant for a few (2-3) days and see if you can get a pair of screwdrivers under the collar and get it to move a wee bit with an eye to working it loose. Having said that, my own experience required taking a scrap piece of sheet metal and cutting a groove in it for a heat shield and quickly/accurately heating that swine collar with an oxy/ac torch and a #4 tip. It came right off and you'd want to have a spritz gun with water to cool things off asap. There's a seal and bushing in that end of the fan assembly so don't go nuts with the heat and you should be good. Took me 2 minutes, literally. Remember, when dealing with old cars, carefully applied heat is your friend.
