Try calling Indigo Ranch studio in Malibu - they have Half of the original console from the Motown studios in Detroit. The engineer there (sorry, forgot his name) really knows his stuff, particularly equipment history.
A few years ago I read an interview with Mike McLean who was chief engineer at Motown for quite a while. He discussed many, many things including: building the 3 track recorder and....he said the vocal chain from the 3 track period on was a C-12 into an Altec 1567A into a Fairchild compressor. He *may* have said the mic was a U67, but I'm certain about the Altec 1567A. I had JUST purchased a few of them and was thrilled by the information.