News:
72 was the 1st year for the slotted bumpers so your rear is correct & not the front or jack as I understand it. for reference see these sales listingshttp://www.rosevillemoparts.com/advanced_search_result.php?keywords=Challenger+Front+Bumper&search_in_description=1&imageField.x=13&imageField.y=13
Is your 71 a late production car?(built in the June/July time frame) It's generally assumed that the bumpers changed in 72 but I saw a 71 Challenger on the cover of Mopar Muscle magazine a year or two ago that had the slotted bumpers. It could have been a late 71 change over.I believe the bumper jack has date codes stamped into the large rivits. Check those out to see when the jack was built.