Hey Mark, welcome to CB!
Seems like you've been cruising the old threads hunting for info. Using the way-back machine by the looks of it too!
Do you have the hub/drum assembly off of the vehicle? Or is it still installed on the truck?
Be easier I would think, if it was off. Presuming it's off and on the ground, have you soaked the junction with penetrating oil and given it some heat? Soak it on the backside too (in the drum) because there's a fairly large surface area there that is pretty sure to be rusted together after (most likely) 41 years or so.
Can you see the seams? Can you see the separate hub flange on the inside of the drum?
If so, it should work at some point. Maybe the heat will do the trick.
Otherwise, you might be looking at buying a hub/drum assembly already put together, to avoid the extra hassle of removing yours.
Good luck! As you can tell by the OP's (original poster) experience, it can take some pretty good hits and still not come apart. Enough to actually break bits off the drum and still not release.
So keep at it. Worry it into submission. But not to death... ;D
Heck, maybe put a couple of the studs back in with some nuts on them and crank 'em down to kind of "flex" the drum in the opposite direction of what you're trying to achieve first. Maybe that will break some of the rust free.
Paul