I would think a thin cold chisel would separate the hub from the drum, then if the retainer/s is present (doubtful on a 68) I grab and twist to break them off (only there to hold on drums before assembly). Like mentioned above if drums are worn the brake shoes may have to be backed off (using a brake spoon and a narrow screw driver or 1/8" wire-think welding rod). If the drum is rusted to the axle hub you may have to heat the center, around the joint, to release the drum. After removal, remove the 5 3/8" retaining nuts and pull the axle out of the housing. Support the flange and drive out the studs, press or drive the new studs in while supporting the flange. Good time to repack the axle bearing and check the inner seal condition or replace it.
Now, what about the other side? The axle shaft end play adjuster is on the right side. Good luck!
Mike