Looks like the tailgate says GMC.
Also, guessing 41-47 due to the fact that the riveted supports for the fender are located directly in the center of the fender. I believe earlier models had the fender support about 3/4 of the way to the rear of the fender.
I think as long as the fenders aren't rusted through the flanges they are easily worth $50, Just my opinion.
Jeff
