Interesting site...
http://sspcentral.com/library/idaho-sp.htm
For reference, GE radios not Motorola until well after the 90's... that interior has an incorrect radio. GE has been the supplier of PS radio systems since the 1950's according to the radio techs at ISP.
GE Phoenix radios are correct for the Mustangs up until 1989 and then they went to the GE Mastr II with the S820 series head. They still have an S820 setup in their