Hy Thornfield, welcome, all drum brakes that I have ever worked on have had a ridge develop on the inboard edge of the brake drum. In order to remove the brake drum you must back the brake shoes back down so that the ridge on the brake drum will clear the brake linings. As has been stated previously the brake shoe adjusters are fragile and don't always back the brake shoes down, that may be the case here. If that is the case then using whatever force is necessary to pull the drums off over the brake linings may be all you can do, understand that this procedure will damage something somewhere in the braking system. One thing you might try would be to undue the bolts that hold the wheel cylinders to the backing plates, cut the hydraulic line and drive the wheel cylinders into the backing plate, that action might result in the brake shoes collapsing in a bit. Hope that helps, good luck.
