That picture in post number three looks a lot like mine and the countertop in my kitchen!
On the GMC there's two pieces that close out the radiator support.
There's an arch-shaped u-channel that closes out the radiator support,
another piece that attaches to the front of the support (the one in post 3)
And a view of how it looks assembled
[IMG]https://talk.classicparts.com/media/in-the-booth-finished-
1.6787/full[/IMG]
I got mine from MotherTrucker in Tucson, but I'd try Paul's truck parts and some of the other used places. I think I paid about $30-50 a couple of years ago.