Complex sentence: Rather than proceeding with the previously proposed expansion to 45,000 seats, Aztec fans would have to make do with this facility until 1966 when they won their first of three consecutive "small college" (Division II) National Championships.
Split into simpler sentences: Rather than proceeding with the previously proposed expansion to 45,000 seats, Aztec fans would have to make do with this facility until 1966. During this final year in Aztec Bowl, the Aztecs won their first of three consecutive "small college" (Division II) National Championships.