Since the mid '70s, Ford has had more suspension and steering part failures than most other manufacturers combined. You should have those systems inspected at a tire and alignment shop at least once a year. Most of the time you'll have some warning in the form of clunks, squeaks, or other noises. Those should never be ignored.
Depending on the size of your truck and the steering and suspension systems used, the primary suspects are ball joints and tie rod ends. Most of the time the ball joints separate leading to loss of control and a crash, but if it is still just sloppy, it can allow the spindle to tilt until the wheel or brake rotor rub. A tilted spindle can also turn left or right on some systems, making the steering wheel off-center, and that tire will walk toward or away from the center of the truck. Once the sidewalls can't flex any more, it springs back and causes that wobble you mentioned.
At the mileage you listed, you should have had most of the suspension parts replaced a couple of times already. If not, you definitely got your money's worth out of them.