The easiest way to tell if you have the late floor pan in the access holes location for the shocks. If they are on the top it is an early style if the access is at the rear for the shocks it is the very late pan that is much the same as the 1972 pan. In 1971 Challenger had three different types of bumpers for the front and two different for the back. My Challenger has the slotted bumpers both front and back.

Not near any of my information on build dates to be exact, but Furyman is likely correct for the SPD of April 15. All the people even BHs Hemi Challenger that have a SPD of June 16th those Challengers were likely not built on that date and were between 7 and 14 days later. Remember the Number on your Broadcast Sheet and Fender Tag is a date Chrysler assigned to the build information but the plant was running well behind these dates for at least a month or more. So what I am saying your June 16 Challenger 616 was likely built around 624 or later.

All these Challenger likely would have the 1972 style trunk floor pan, slotted front and rear bumpers and a lot more of the 1972 Challenger build. My Challenger has the studs on the fender were they attach to the inners. Yes my Challenger has a June built Door tag but the fender tag states it is a May built Challenger. I have seen this on a lot on late May built Challengers.

There you go Mr.M

My Challenger has 72 bumpers on it. Car has never been hit. Bumpers have never been off the car.