Brake adjusters on my 51 1 ton are at either end of the wheel cylinder and operated by a nut on the back side of the backing plate. Not sure if you have the same Huck brakes I have or later Bendix? If Bendix the adjuster is a star wheel at the bottom inside, operated with a brake spoon pry-bar thing.
While trying to remove the drum be kind to it, they are becoming increasingly hard to find.
