Jim, did you ever, during your restoration, get involved in the audio side of things?
The reason is I have one also and I'm looking to put the original head unit back in (once I know what it is!)
I can find the 7 way power plug as usual (I used to fit sound systems into Cosworth back in the late 90's so I've cut more of them off than I care to remember) but there's no sign of an amplifier in the passenger footwell behind the kick panel as I seemed to remember there would be.
Also, I can only find 4 wires for speakers not the usual 8.
I can find no evidence it had a CD player below or Graphic Equaliser.
All very odd, wondered what you had found in yours?
Cheers,
Justin