Whats the difference between 66 & 69 steering Columns?

I can shed a bit more light on the guts of the steering wheel - the copper horn contact which is secured to the wheel with that HD round spring is the same size for my early A wheel, the 69 wheel and a later 70's Tuff wheel adapter - about 2 inch in diameter. FWIW the diameter of the area of the steering wheel that sits on the collar for the early A column is 3.5 inches. For the 69 and Tuff wheel adapter, it is 4 inches in diameter.