Interesting. I wonder if the 69 installation was changed from Chevrolet to Fisher because of the work involved. From the drawing, it appears that the only thing Fisher installed in 68 was the "Retainer" for the Escutchion. The rest (I'm assuming) was installed by Chevrolet. I'd like to know if the D33 option shows up in the 67 AIM. This might tell us if a change was made in "who" was responsible in installing this option. If it does show up in the 67 AIM, I would bet the responsibility went from the Chevrolet line to Fisher because of the time and work involved.