Someone asked this question. I have used an automotive gear puller to get crank arms off. They are available at auto parts suppliers or Sears OTC makes a nice one for around $26.00 It works but usually the puller arms ding up the crank arm but the arm is no good once the threads are gone anyway. I guess you could reuse it if you wanted to. I can't think of any other way to pull it without the threads.
Sam D.