This is interesting. This question is in regards to a 68 Firebird, so I figured it would also apply to a Camaro.
While I got more responses here, the couple of responses I got from the "First Gen Firebird" site said there was no undercoating applied. I find it hard to believe there would be a different process at the Fisher plant for Camaros and Firebirds.
I am waiting for a response from a guy who has an original, unmolested Firebird. Curious to see what he comes up with.
Thanks everyone!