I have a 6' length of 3" heavy wall pipe that I use as a slide hammer/battering ram to drive the drums off. Laying under the truck I rest the pipe on top of the leaf springs and take good aim at the back edge of the drum and give it heck...two or three good hits on the back edge and then two or three on the front edge to walk it off...it's a slow process, but it has worked for me on several occasions.
Pulling the axle and removing the outer bearing will allow the entire hub to swivel and move more which may help. You'll want to remove the hub anyway for better access to the brakes.
Mike B
