Complex sentence: In 1967, Porsche lobbied the SCCA to reclassify the 911 as a sedan, and then went on to dominate the Under 2.0 Liter field, winning the manufacturers' championship over Alfa Romeo.
Split into simpler sentences: In 1967, Porsche lobbied the SCCA to reclassify the 911 as a sedan. Then dominated the Under 2.0 Liter field winning the manufacturers' championship over Alfa Romeo.