The slotted Bumpers came out in June of 1971 on a Challenger. The slotted Jack I believe is a 1972 use. Barracudas did not come out at the same time but I do not know a date for this. My Challenger has front and rear slotted bumpers and is an early June built car. It some times is hard to come up with a date because Challengers were running over a week late at this time so a Challenger with a example May 24th SPD would of been built in June but a Barracuda with the same SPD May 24th was built in May..