Monogram didn't specify a model year for its 1/24 scale Trans AM Pontiac kit, but I think their was intent was that it could be built as either a '77 or '78, depending upon which hood bird decal the builder chose to apply. Here's a look at the original issue, kit number 2247, from 1979, courtesy of various eBay listings:
I never realized two hood birds were included until just now, but it does appear both '77 and '78 style birds are included:
But wait!, there was also a companion Trans Am Street Machine kit, number 2258, also released in 1979, which featured a custom nose piece, hood, six-spoke wheels, bucket seats, turbocharged induction system, and "Turbochief" decals:
The stock version has been reissued a few times since 1979, and now exists as a 3'n1 kit, shown below in the "Warbird" box:
The Street Machine version was only issued once, and never seen again... not necessarily a bad thing.