I finally added the bibliography of historical sources used to produce the car index.
In 1974 Post-Era Books compiled a collection of literature from the Duesenberg factory and published them under the same cover. This is the source for "Duesenberg Ads", "Model J Instruction Book", and "Model J Specifications".
Marshall Merkes was once the owner the Duesenberg marquee, operating out of Los Angeles selling parts. In the early 1960s he published a series of bulletins about restoring Model J Duesenbergs. Some of those bulletins are reproduced here.
Lassiter Hoyle provided the list of gear ratios. He has always had the ability to calculate gear ratios in his head, and probably produced this chart from memory. I used this chart to check the accuracy of odometer and speedometer on our car (and which rear end we have), but I had to come up with a formula to calculate speed based on the revolutions per minute (RPM). The chart uses 4200 RPM exclusively, a figure chosen because it is used to specify the expected horsepower output (265 horsepower at 4200 RPM), but that's not very useful at normal speeds. We have yet to drive our car over 3000 RPM, nor do we have any intention of doing so (that's almost 80 mph). By the way, our instruments are the old style barrel type, and wobble enough to make accurate readings less than 10% impossible, but the they do prove reasonably accurate.
Ray Zahn's list was made in 1968 and includes detailed ownership information for many of the cars. Its primary shortcoming is that all chassis numbers are omitted; so it is sorted by engine number.