Complex sentence: The final A10 development, and fastest in terms of power and performance, the 1962 BSA Rocket Gold Star, which fitted a tuned A10 Super Rocket engine into the well proven BSA Gold Star single frame.
Split into simpler sentences: The final A10 development in terms of power and performance was the 1962 BSA Rocket Gold Star. A tuned A10 Super Rocket engine was installed into the well-proven BSA Gold Star single frame.