To know what size motor *fits* a specific 1980 Camaro, you need more information:
* Is it a stock car? If so, consult a 1980 Camaro parts catalog or a reliable online resource to see the factory engine options.
* Has it been modified? If so, there's no way to tell without inspecting the car or knowing its history. The engine bay can accommodate a wide range of engine sizes with appropriate modifications.
In short, the question is too broad. The range of possible engine sizes is vast.