Looks like Motorola made that radio for Ford,
Mustang Radios, 1965-1973
I don't see a schematic there. I have the reprint of the 69 Mustang 5 volume set of factory service manuals somewhere, they have all the wiring schematics in one. I have to see if I can find where I put them since I don't own a 69.....yet

. But if you have them or someone else does the answer will be in there. I'll look around today when I get a chance.
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1968 Mustang coupe, Acapulco Blue, 289 2v, C-4, Power Steering.
Hopefully a 1969 convertible or Sportsroof (non Mach or Boss) for next Mustang project
Trying to find my father's 1973 Mustang Grande he bought brand new. 3F04F126773 last known registration and title was in New Jersey, 1982.