Well since the cab is under wraps waiting for the bed to be finished? I'll put these pics up. They're not the best (camera phone) but they'll have to do until l can get some better shots later.
As you can see from this pic. The "curve or bend" of the grille does not fit a 73-80 front clip. There is no curve to the grille area whatsoever? So the center pokes forward and the furthermost left & right ends are recessed into the grille area. You can also see the gap it creates at the top center.
And here you can see (try to look around the distortion from the light) that the grille pokes forward in the center like a 81-87 so it would never fit properly. Flush with the grille surround.
I can edit the images and insert arrows pointing to what I am trying to show but I think you can see it pretty clearly.