I was looking through some old family photo albums and came across a few pics of a 69 or 70 that my grandfather used to own. I believe they were taken back when the truck was still fairly new. They're a bit out of focus so it's hard to see some of the details but I figured they might still be a helpful reference.
As
Steve Hafner posted earlier, the black paint on many under-hood items is "glossier" than many people think and this last pic backs that up ... especially the air cleaner assembly.
I also found it interesting to note that this particular truck doesn't appear to have any writing visible on the firewall like many of the others I've seen. That's probably something else that varied from assembly plant to plant.
As for the hood hinges & hood latch assembly that were discussed earlier, I've cleaned up a lot of them on other 60's/70's GM cars & trucks (as well as come across a few NOS examples) and the majority of them had a gray or black phosphate type finish.