The 1/2 ton king pin bushings are floating bushings. They do not need to be pressed-in; however, they should not "wobble" when in place. If you have almost no wobble (just up-down movement), you are most likely OK.
Over-sized bushings are for over-size king pins. You need over-size king pins if the king pins wobble in the holes in the axle. Did you test-fit the king pins in the axle before reassembly? How tight were they?
