1967-4 would indicate 4th quarter (Oct Nov Dec) of 67 meaning for a 68 model year
1967-1 would indicate 1st quarter (Jan Feb Mar) of 67 meaning could be for a 67 or 68 but most likely 67 model year
1967-3 would indicate 3th quarter (Jul Aug Sep) of 67 meaning for a 68 model year
As I recall model year ends in June and starts in July (someone correct me if i'm wrong here)