225 to 400

If it runs, $500 is close to fair. If you plan on rebuilding it, $2-300 is much better. I was fortunate to find a core 400 for my son at a half-price day at local yard a couple of years ago. Turned out to be a standard bore motor that looked to have never been apart. Cost me a shade under $100 (well, cost him). It's unlikely you will find that kind of deal, though.