The GTO scoops are different than the Firebirds. The 2 hood scoops on the Firebird are spaced much farther apart than on the GTO, and so the scoop inserts themselves have a different taper. They will not interchange.

The entire 1969 Firebird 400 Ram Air assembly is reproduced now, from the flapper assembly to the pull cable, but it's very expensive. The 1967/1968 Firebirds did not use a flapper assembly, the scoops were just cut open for the Ram Air cars.

One thing you'll notice with a true Ram Air system is that the engine is quieter at part throttle, and especially at full throttle. That giant "roar" from a Pontiac V8 with a Holley or Q-jet is very muffled with Ram Air, as the carb is only pulling air through those two hood scoop openings. It will be as quiet as a dual snorkel air cleaner, verses a 360 degree element.

While the open scoops of a Ram Air system don't actually provide a ram effect, they do pull in cool air. There has always been some debate as to how much air can be drawn through those two GTO (68-70) or Firebird (67-69) hood scoops. The total area isn't that great.

Just a note, be cautious of buying the cheap repro plastic scoops that some vendors sell. On a hot day, and with your engine temp at 200+, they have a tendency to warp.