There were very few heads that were specific to a model of car. None were specific to the Firebird. (The block code is the most specific.) Dates do not separate one model from another, but they can elminate certain models. The date code indicates when the part was cast.
Since production of a particular model year started in July or August of the previous year (usually), you can kinda bracket which year the heads were for by the date code.
Carburetors were different part numbers, as well as alternators and distributors.
