I don't know exactly how '51 drums are fitted, but here are some general thoughts, because I have sure fought frozen drums alot here lately on a fleet of woods derelicts I have bought and hauled home. Firstly, make sure the holes around the bottoms of the lugs are wirebrushed as clean as possible, and around the center. Next, does it have the little pins that go through the shoes through the backing plate and you can see the "heads" on the backside, if so clip those off with wire clippers or dremel. lots of penetrating oil in every fashion into every crevice. I beat on the drum face between the lugs and some on the sides (you're not supposed to do that) and alot on the back edge, and use a serious hammer (I use a 4 pound). I also use combinations of flatheads and prybars to try to get into any crevice.
If you can get it moving any and can slip a small prybar in the center hole edge, you can leverage it pretty good.
It's a hard fight no matter what and don't forget rust around axle hub and lugs can thwart every effort.
