I believe that your AM-FM may be earlier than Marty suggested. I entered the Model Number shown in one if your pictures, in Sam's Photo fact Site. It shows that this radio is covered by Photo-Fact AR-280. Of course it doesn't give the date, but says that you can Download it for $22.00. When searching for specific radios, and finding what AR # they are in, I usually check to see if, by chance, the hard copies might be available on Ebay. Sure enough, this one is. (first picture). In looking at its description, it shows that it is the First Printing, 1979. Thus this radio is at least 1979, and possibly a little earlier.
If you want to purchase it in order to find out more about the radio you have, here is the link :
https://www.ebay.com/itm/Sams-Photofact-Auto-Radio-Manual-AR-280-First-Edition-First-Print-1979/253394194812?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649, I think the total is about $9 including shipping, for the hard copy original.
This also might be a good time to share this list of 1964-1/2 - 1973 Mustang Radio Identification that I got years ago from Dave Hammar's old Aloha Mustang Site.
Enjoy.
Bob
