I did notice that 8568 argent silver is gloss. It can be flattned. Ask the paint supplier about that. Also I can't remember for sure, but I think there are two argents. A light one and a dark one.
Here are a few threads with some information on argent silver
http://67-72chevytrucks.com/vboard/s...d.php?t=346227 post#23
http://67-72chevytrucks.com/vboard/s...d.php?t=443225
http://67-72chevytrucks.com/vboard/s...d.php?t=446597
http://67-72chevytrucks.com/vboard/s...d.php?t=398402
Let us know how it comes out