If the kingpin hole in the axle is "wallowed out", another option is to ream the hole (eye) for an oversized kingpin (if the hole is not oversized by more than 0.010").

Another cause of looseness is that many steering knuckles have "wallowed out" kingpin bushing seats (I am not sure of my terms here). New king pin bushings then move around and the joint is loose (as described by John). Some people have luck knurling the bushings and pressing them into the seats in the spindle - I have never had luck with this. I am not sure if the bushing seats can be drilled for larger bushings (larger outer-diameter).

Tim