How do you remove rear brake drums from 1988 GM 1 ton truck?

1. Jack up the rear of the truck and support it on jack stands. 2. Remove wheels. Spray penetrating oil on the wheel lugs. 3. On the back side of the drum you'll see a oblong rubber seal. Take it off. 4. Reach in with a flat screwdriver and back off the adjusting screw until the wheel spins free. If it spins harder, go the other way. 5. When it spins free take a rubber or wooded mallet and commence to beating on the back of the drum around the outside edge. Beat in different places arround the edge. Beat HARD. It will eventually break free.