Go to a Wal-Mart and get a couple of spray cans of PB Blaster. This is the best penetrant I have ever used. It seems to dissolve rust, even between tightly fitting parts. Let it soak for a couple of days, spraying it twice a day. Now apply the heat, and use an Acetelyene torch. Forget about Propane torches, not enough BTUs in there. If you don't have an Acetelyene torch, go to a plumbing supply store and get a cylinder of Mapp gas for your propane torch. It works almost as well as Acetelyene.
Be sure to follow the advice about how to use the puller, they are right about breaking the pulley. Don't ask me how I know. :o(