To my knowledge there is no known November 1, 1929 Chicago Service Letter. The KNOWN Chicago Service Letters go from December 27, 1929 through September 29, 1931.
Just what is contained in it that you are wondering about?
Apparently there is a list of parts to install the 4-speed transmission in the 28-29 AA.
The Jan 17, 1930 Chicago Service Letter states "Our letter of Nov 1, 1929 listed the
transmission at $42.00 subject to 25% discount to dealers and additional necessary
parts to make the change, totalling $22.47."
Might want to give Neil Wilson of the Double AA Truck Club a shot at that question if you havent already...he might have the answer for you that you are looking for.
Thank Vince. The list I'm looking for would have been before A-7090-C, A-7085-E and AA-7085-B were available I think. Neil Wilson said when they did the 4-speed conversion they replaced the 3-speed coupling shaft with the one for the 4-speed.