While the B16 engine is a more powerful engine than the stock engine in the Toyota Starlet GT, it is not a direct swap. The B16 engine is wider and taller than the stock engine, so it will not fit in the engine bay of the Starlet GT without significant modifications. Additionally, the B16 engine has a different transmission pattern than the stock engine, so the transmission will also need to be changed.
Overall, while it is possible to swap a B16 engine into a Toyota Starlet GT, it is not a simple or straightforward process. It will require a significant amount of time, money, and effort to complete the swap.