I "think" there may be some info on this site that a search may give you some results but if not maybe look in some of the first generation Camaro sites or even the yenko.net site
Personally I like seeing different gloss/sheen on the black underhood parts and not just have it all one type. What is original, I cannot say but there is documentation out there or a least a good consensus.
I looked at a 68 Nova over the weekend and I could tell things were repainted at some point but at least things were broken up with semi gloss, gloss, and natural finishes.
I can't say for sure on your car (or even the 68 I looked at) but on this 68 I looked at I could vagely see a sticker on the wiper motor and if it is anything like the original from my 74, I'm thinking the wiper motor also had a sticker/decal on it. Who knows if these are even reproduced.