I had one on the '73 I'm working on now that wouldn't come off, even when I had the tire shop try. I drilled two small holes along one "side" of the lug nut, being careful not to hit the stud threads or drill into the wheel. I then cut between the holes with a small angle cutter as far as I could without touching the wheel and finished off with a cold chisel and hammered till I split the lug nut (they're surprisenly soft). I would only recommend this if your only other option is to pull the spindle and throw it and the wheel away, but it worked for me. Good luck.
Steve