Are there any pics to illustrate the difference between the KKX and the other big spindle?
Not sure if there is a difference other than the markings between the early KKX and the "Big suspension" D0 versions that quickly followed
As for the difference between the regular and big suspension:
Other than the castings, a section of bailing wire wrapped around the upper part of the spindle as a quick identification for the line workers and paint marking differences it comes down the the difference in measurements of the bearing races - not something that would stand out if looking at one IMHO. There is a document posted in the 69 Library section concerning some screw ups on the line when the new suspension option was released concerning a group of cars where the parts (wrong rotors on the wrong spindles and so on)
Titled
69 Disc Brake Spindle and/or Hub and Rotor Mismatch Issue Believe there are some close ups in the thread where I dissassembled the front suspension of my early 69 Boss did a little cleaning and reinstalled. Car has about 30K miles on it