Back the nut off until it is flush with the threaded end of the steering shaft and use a dedicated Model A steering wheel puller. The center portion will push against the nut, protecting the end of the steering shaft. If you try to beat the steering wheel off from behind, you'll end up chipping the heck out of it, as well as possibly breaking off the end of the steering shaft. Do NOT use a "knocker' threaded onto the shaft! This will for sure break off the end of the steering shaft without getting the steering wheel off. Either borrow a Model A steering wheel removal tool from a friend or local club, or buy one from a Model A vendor. If you plan on restoring other Model A's, this is a great tool to have handy in your garage.
Marshall