Yikes!!! That thing is like a mini-monster truck!!! stout, stubby, stump-puller, whatever you want to call it, just call it Sir! Very cool.
We had 2 stuck drums recently on a '39 ton and a half. My mechanic has a hell-acious set of pullers. Used a big set on each wheel - don't remember if it was 2 or 3 jaw. Got the hubs off, slightly bent one of the brake webs in the process, ended up being no big deal though.
Patience is a virtue, if you have the luxury of time. Like baramos says, better living through chemicals. Don't worry about soaking the shoes, as they'll either clean up or you'll replace them. I'd spray liberal amounts of Kroil or penetrating oil all around. Let it soak in for a day, then spray again, wait another day. Then go for the wedges idea. 3 or 4 spread around the edge, tap slowly but firmly on each in turn. If it feels like it's still not giving, leave it under pressure, and come back and tap on each wedge every few hours. It took time to freeze on there, gonna take time to un-freeze.
In the end, there may be no option but to force it. Try everything else, then be brave. Gotta come off if you want it reliable, after-all . . .
My thoughts, anyway.
-Michael
