[Kurt S]

I am the person the prior owner of the car first contacted when he realized he had #1. I don't question the car - it's real. I'd suggest posting some in-process pics of the original fenders and quarters to allay the naysayers.
I highly suspect this car got a much better resto than the #1 and #2 Firebirds got.

Tag - no, you never mentioned it was a new computer system. It's original, but strange.
Decklid - that's actually the 2nd version of the lid. The first version has no access holes (what were they thinking?) and is only on very early cars. Looks like the original was cut as black69 noted, but there wasn't much to go on.
Sheetmetal - not surprising they were tagged and not stamped. Bet some were stamped (because they are part of the die design), but many stamps are hidden and hard to find.
Block should be stamped.

Posts like Tom's aren't helpful to the conversation, IMO.