Paul:
1970 was the only year that you could get a 12-Bolt in a Firebird. It was included as part of the Trans Am package. One of the reasons that '70 T/As are so very cool! Can you tell I have one? Possibly my favorite car, 31,000 Miles, Original Paint, Born with Drivetrain, Ram Air III, M21, 3.55:1 Posi 12-Bolt and White with Black Interior. I'd give an appendage for a Ram Air IV car though.
Ed