Rusted TIGHT rear drum removal?

[pocketrocket]

I will be installing rear disc brakes if I can get the old drums off! I have taken everything up to a 10 lb. sledge and they won't budge even a little. I have checked the trans, and it's not in gear, but there is not ANY play in the drum at all. My question is that if I am getting rid of the old back plate anyway, can I cut thru it and , with the spindle nut off, will the whole assembly come off? Does anybody have any other ideas? I really need some help. Thanks to all for any response!!!!! Oh, by the way, the engine is not in the car. I tried using a makeshift puller but it only pushes the axle in!