Larry is right on it I think. It looks like as the brake linings wore they were adjusted out to compensate. If the drums have been turned (a common practice) as LarrBeard suggested, it would exasperate the situation. These brakes are discussed thought on many forums. the reason is they can be a bit "finicky" to adjust. You will need to adjust the shoes all the way in as covered in the manual. Then the drum will go on.

If you have a Universal Service Manual for Jeep Vehicles, This is covered in section P-6.

There is a discussion on brake adjusting here. https://willysjeepforum.kaiserwillys...ghlight=brakes

If you search this forum for "Brakes" it comes up a few times.