I had an identical pickup to this when I was a kid. and I put those exact mud flaps on a month after I bought it from my uncle. he bought it new it had 22,000 miles when I bought it from him in 1977. I sold it to another uncle in 1980 and he sold it about 20 years ago and I never saw it again.
Is there a few holes in the front of the bed on each where I had brackets for my whip CB antennas ? that would tell for sure.
Sure would be neat to know what happened to it. I sold it to by a '78 CJ5 Renegade, that was a big mistake I hated it.