I'll throw in my few pennies ...
The brake drums are made of cast iron. If its alloy composition is correct and properly cooled after casting, gray cast iron is produced. It should be like that, it has a high coefficient of friction, but it is soft.
Such a correct casting should be seasoned for several months - the longer the better. Only then is it machined to the required shapes and dimensions.
According to my observations, this is the production technology of the original drums sold by Ford, but they are very expensive. Ford original brake drums are correct.
The problem starts with replacements. They may have the wrong composition (too little carbon) and cooled down too quickly - then no gray iron is produced, but white or mottled. Such a brake drum will be ... tragic. White cast iron is very hard and has a low coefficient of friction.
Even if the castings are correct, substitutes are not seasoned, but are immediately processed and sent for sale.
This is where our problem lies. Such drums are most often ovalized, curved or warped with respect to the centering hole.
There is a workshop in Warsaw specializing in Transits for 40 years. Here, the brake drums are first mounted on a precision tool lathe. The base is the central hole, the friction surface and a contact surface on the hub are rolled. The drums processed in this way are attached to the car, but with the recommendation that if there is still vibration, then after two or three months the gentle rolling process must be repeated. That's how I had cheap replacement brake drums installed in them and I can say that it was good.
Regardless, you can move the wheels front to rear, you can try to turn them in relation to the brake drum, or you can try the same with the drums in relation to the hub. I've done it many times - sometimes even with positive results, Sometimes ...