Okay, the cat who sold me the panel bus had a couple of single cabs near that vintage.  They were both pretty complete, with dropgates and such, but he might be parting them out.  E-mail hassellevw@aol.com.  Tell him I sent you and you're from the Volks Folks.  He's in Meridian, Mississippi, and he said he's coming to our show.  He came last year, too.