Doug, Your measurement for the "old" kingpin of ".877 inches" most closely matches the dimensions for a .010 OS (oversize) kingpin set. An original GM .010 OS king pin replacement kit (GM# 609882) shows the king pin dimensions to be .876" X 5.31" long in the Master Parts Books. Trying to replace an already oversized king pin with the original smaller diameter king pin will leave you with an even worse wobbly condition. If the king pins are sloppy with the old kingpin and bushing set, where exactly is the slop? Is it in the bushing to pin fit, or is it in the pin to axle bore fit? I would suggest you check the fit of the old pin in the axle shaft hole and see how tight/loose that fit is before moving on with more questions.
I would also mention that the math doesn't seem to work with the old pin diameter (.877 inches) and the old bushing inner diameter (.866 inches). The pin wouldn't fit into the bushing if the inner diameter of the bushing is smaller than the pins outer diameter. A typo perhaps?
Edit: Fibonachu beat me to the punch on this last thought.
