The LS1 engine is a modern engine that was not available in the 1979 Trans Am. As a result, you will need to make some changes to the engine mounts and transmission in order to fit the LS1 engine into the car.
Additionally, you will need to upgrade the fuel system and cooling system in order to support the LS1 engine.
Overall, installing an LS1 engine in a 1979 Trans Am is possible but will require some work. If you are not experienced with this type of modification, it is best to consult with a professional mechanic.