Kevin, I've checked the Radio section already, no luck - thanks for the tip though.
Richard, Becker Autosound wiring diagrams are just for the back of the radios, I do have a request in to them for a schematic, haven't heard back yet.
Oz, I've considered joining the Radio Museum before (I fool around with old tube radios), but their membership requirements are a bit too draconian imo. Keeps out the riff-raff I suppose. I think I found the correct schematic there, though I was hoping that someone here at SL113.org might have one already in hand....
Thanks for the suggestions,
Wil