I'm going to say that you might want to pull all 4 drums and be sure the brake shoes and wheel cylinders are not stuck in place from sitting.

I'd also pull the master cylinder away from the booster and see if the pedal will travel the full stroke. I've seen the push rod get stuck inside the booster, as well as between the brake pedal and the booster. If you move the master cylinder out of the way, the brake pedal should freely travel the full stroke the pedal will allow. A fully bled and properly adjusted drum brake system usually doesn't have a lot of pedal movement, but they usually grab pretty good.

Lots of stuff gets stuck from sitting around a while without being used. Gene