One of the key things that I have learned about brakes is to expect the worst. A lot of patch work and poor repairs could have been performed over a 50 year period. My recommendation is to remove all wheels/drums and inspect the brakes carefully. It's OK to give it a once over to look for obvious things as you have done but it doesn't tell much of the story. I have actually removed 3 drums and found pristine brakes and the 4th one to be totally shot. Good brakes and a properly adjusted parking brake should hold in both directions.
In many cases on vehicles that sit for long periods of time brake linings become too hard and loose their friction coefficient to work properly.
Fred
