I was just discussing this a bit with my dad earlier tonight...and apparently my truck, a 1970 GMC, came from the dealer with the 1971-72 style blacked-out grille!
Unless my grandma has some more photos of it somewhere, though, I don't have any real evidence. The one old photo I have of it before my dad had the entire grille rechromed doesn't show the frontend at all. It was apparently black painted onto chrome...
Now, BEFORE you all go telling me I'm crazy...I've got a few theories as to how it could've happened. The basis for all of these is the fact that it was purchased in October of 1970, when the '71s would have been out for a while. (My grandpa must've gotten a smoking deal on this truck, given that he pretty much hated it - four wheel drums and a 3 speed column shifter. I wonder what he would think of it now.)
Theory 1: The truck (which has a sequence number of 60576) was built so late that they were already switching over to the '71 style grilles.
Theory 2: Sometime before it was sold, the original grille was damaged somehow and replaced with a '71 style instead.
Theory 3: For some reason, the dealer installed a '71 style grille to make it look more like a '71 than the still-hadn't-sold '70 it was.
They're all a bit out there, and I still have no real evidence of it; I was about 6 when my dad went through it all the first time, so I don't remember much about it (aside from that you could reach right through most of the passenger side panels, lol)
------------------
Project 1970 - soon to be seen at
http://milhouse.treylis.org:81/