OK, on the link you provided, take a look at the eighth picture down, actually it's a drawing titled "This picture applies to any kingpin Dana60 front axle".
You will notice that a center line drawn through the center of the king pins is on an angle from vertical. By the time this line extends down to the ground you will see how it is close to the center of the contact patch of the tire.
If the center of your tire is very far away from where this centerline hits on the ground then you scrub the tires when turning, and it could act funny when driving.
So the wheel that was used with each particular hub, spindle, and knuckle combination when new takes this into consideration. And using wheels with drastically different back spacing, or a wheel and spacer combo that results in different back spacing, is less than ideal.
Does this make sense?
Grigg
