OK, dimensions for 1/2 ton GMC, model 100-22 are:

King Pin: Length 5-5/16"

Diameter (Standard): 0.8660"-0.8665"

Knuckle bushing Length: 1-5/16"

I.D. : 0.867"- 0.868"

Axle I-beam allowable twist: 1/2 degree.

King Pin hole I.D. : 0.867- 0.8677

smile