Very nice car. Not rare in its won right but the fact that it has been kept so close to how it was originally equipped - that makes it rare.
As others have mentioned...
bumper rub strips - can't remember seeing those on any car other than a 73. Vertical bars with rubber were also on some 71 and 72's, but I don't think the ones with the strips - strps were bolted onto the bumper.
That clock was definitely added later - in your high-res pics you can see glue and touch up paint where it was installed. Doesn't look bad just not original to your car.
The AM-FM was most likely came from another car.
If a customer wanted to change the radio setup on a new car the dealer commonly sent the car to an outside vendor who offered a 'package' for the customer just as trim shops would add vinyl roofs, etc. The cost of a Ford factory radio did not allow near as much profit as an outside vendor would offer.
Money means everything to a dealer. My father was in the car business for many years.
But...
Any owner could go to the dealer's parts counter and order a factory radio and either install it himself or hire a radio shop to have them install.
One big problem with that scenario - back then the factory radios were poor performers as compared to the aftermarket radios. This continued for a long time. I bought and installed a Pioneer Supertuner for the convertible back in 1977 and would have never traded it for any factory radio. Now I'm going back with a factory radio.
Ray