All I can tell you all is this. After taking my 69 Camaro to the Norwood Reunion last July that was hosted by author and Norwood expert Phil Borris, and listening to the workers and their stories about that facility, don't ever say "that was never done at the factory". These ladies and gentlemen told stories about the cars that came out of Fisher Body and Chevrolet that would blow away all the so-called experts claims of authenticity.
As an example, workers would run out of parts and improvise. Camaros and Firebirds came out of Fisher Body with a floor pan for a column shift Camaro and the chassis was assembled with a 4-sp. What did they do? They called for a guy named Chisel Man. He had 25 seconds to make a hole where there was none. Another was how employees who had ordered cars would have options installed that WERE NOT on the order paperwork by friends "on the line". True stories.
So, while some of you "experts" will contradict the authenticity, remember, sh*t happened on the line that unless you were there, don't ever say never! ANYTHING was possible.
ps. I won't even get into the Canadian Built SS 427 that I sold a couple of years ago!