Early built 72 with 71 cab?

[JQ-72]

Discovered this interesting little truck this week. I heard that a guy close by was cleaning up a property and was hauling scrap off. There was an old Chevy truck that was pulled out of the weeds. I asked around and found out who owned it and told him I was interested in it. He let me look at it and told me at some point someone has stolen the doors, tailgate, VIN plate and glovebox door. Also, kids had knocked out the windows. I looked over what was left of it and saw the raised pad for the rear view mirror and told the guy it was a 71 model. I bought it, drug it home and started tinkering on it, even got it running! After noticing the 72-only longer alternator upper bracket and a few other clues, I checked the frame VIN number - 2S100077. This truck was the 77th unit built at the St. Louis plant. What’s left of the truck appears to be untouched - original paint, tower clamps under hood and GM stamped radiator hoses. Could it be that GM used a left over 71 cab?