With the car on axle stands
Give the brake drum a couple of hammer blows (not steel!, try to avoid the rim cast into the brake drum.
Slacken the brake adjuster right off and I mean right off! Remove the 1/4" set screws, there may be up to four of them.
No need to remove the slotted screw as earlier posters have said, they are there to locate the drum.
No, no and no. The slotted screws are countersunk into the drums - if you leave them there, you need to take the axle apart. No one does it that way.
This diagram is from a Rimmer Bros catalogue is of a Triumph Spitfires back brakes, but it is a quite an accurate drawing of a Morgan disk wheel set up too. The only difference is part number V5435 is slotted, not posidrive as in the drawing.
Triumph Spitfire rear drum brakes
Please, please Stevemag, post a picture of your car jacked up with a back wheel removed.