Dennis,
The term oversize refers to the fit between the pin OD and the AXLE EYE ID. Your choice of oversize will depend on how worn the axle eye is. When you buy a king pin kit, the bushings are suppose to fit into the spindle properly and the ID of those bushings are manufactured to fit the OD of the supplied pin perfectly.
All kits for your rig will have the same OD on the spindle bushing...no kits address a worn spindle bushing fit, they assume it is fine and focus on the pin to eye fit.
The only item that is reamed or machined in a CONVENTIONAL king pin install (on your truck) is the axle eye.
If the spindle bore is worn or egg shaped, this is addressed separately on a custom basis...you will have to get together with a machine shop to remedy the problem. Spindle bores will have to be machined round, true and parallel to each other and bushings will have to be made and installed. Once the spindles are kosher, the axle eye can be addressed. Depending on the fit of a standard pin in the eye, your king pin set will be STD or .010 OVER, or whatever will fit properly after a axle eye cleanup.
Has this confused you...I hope not.
Stuart
