Complex sentence: For the 1968 model year, GM had instituted a split-wheelbase policy for its A-body intermediate cars: 112 in (2845 mm) for two-door models, 116 in (2946 mm) for sedans and 121in for station wagons.
Split into simpler sentences: For the 1968 model year, GM instituted a split-wheelbase policy for its A-platform intermediate-sized cars. Two-door models would have a 112 in (2845 mm) wheelbase, 116 in (2946 mm) for sedans, and 121 in for station wagons.