Complex sentence: It replaced the First Class Award, which was GSUSA's highest recognition from 1963-1980 and before that the Curved Bar award and before that the Golden Eaglet award.
Split into simpler sentences: It replaced the First Class Award, which was GSUSA's highest recognition from 1963-1980. That award was preceded by the Curved Bar award, and before that the highest recognition was the Golden Eaglet award.