Ed,
I tried to post the following text on Friday, but it didn't go through for some reason.
I've long suspected that you're right about the likelihood of finding one of those sets. They were rare, they didn't work well (at least not by the standards of even two years later), and people gave up on them. The 1932 Cadillac radio eliminated the "B" batteries and introduced superheterodyne technology. It was a far better radio, and some people even retrofitted those into 1930 or '31.
The picture I posted of the set came from a page out of the November 11, 1929 issue of Radio magazine that someone had posted online. There's also an article from the January 1931 issue of Cadillac's Accessory Facts, a publication that Cadillac sent to dealers to pump sales of accessory items. However, both documents are in .pdf format and this forum does not consider .pdf files to be "accepted." I'll try to send them to your e-mail address in the CCCA directory.
Joe from Texas told me the long saga of his successful hunt for the radio that's now in his roadster. As an airline employee he was able to travel around the country to attend radio club meets, track down leads, and so forth. He and the late Doug Houston figured out over the phone how to re-engineer the electronics of the 1930 Delco Remy radio to convert it into a really usable set.
Best regards,
Chris Cummings