I have four different sources for advice on shades of gloss and the best is from a GTO publication (HPP I think). I know that the heat box was gloss and the firewall flat to no gloss. I have been restoring piece by piece pulleys/air cleaner/volt reg cover/radiator/etc. Since my car is 100% original (driver) I am trying to stay with paints that keep a little aged look (not to much gloss) but cleaning up the car overall.
At the same time I do not have the funds to pull everything apart, professionally shoot it, to then drag to a show and try to win trophies. My goal is to have and drive it with it cleaned up and running smooth all by my hands.
If I can find the digital copy of the GTO article I will post it.