I think someone posted a part number for a 47-55 3100 king pin set that had over-size outer-diameter bushings (with/without oversized king pins) that might save a "wallowed-out" spindle/knuckle and axle. The spindle/knuckle would have to be drilled/reamed to match the outer diameter of those bushings.

Maybe someone can find that post with the part number?

My observations have been that the bushings/pins get loose and eventually wallow out the spindles, while at the same time wallowing out the king-pin holes in the axle. Poor maintenance/inspections is the obvious cause of the often irreparable damage.

As stated above, over-sized king pins are readily available (sometimes in two over-sizes).