King Pin Bushing Lengths Continued...
 

Well, I had a chance to remove all of the bushings within each spindle I have and here is what I found:

Round Shape Early 1928 Spindles:

Top Bushings averaged 1.1 inches (A-3109)
Lower Bushings averaged 1.1 inches (A-3109)

When it came to the Rectangular Shape Mid 1928 thru production Spindles:

Top Bushings averaged 1.06 inches (A-3109)
Lower Bushings averaged 0.97 inches (A-3110)

Pluck