Here's the thing, it depends on which casting you are talking about.
The Cobra single 4's are the most flat, non-gloss ones. Similar to the oil pans.
The GT500 2x4's have a slight glow to them.
The C60A T/A I have has a definite glow to it so if you ask me, they are all different and there is no standard between them.
Now before the bickering starts, of those three, I have two that are original finish. The C7ZX and the C60A. They are from THIS planet and not delivered here by Martians, and yes they are in New York and no the air in not different here.