The rear harness i removed from a 65 Barracuda I parted out had the connector farther forward and tucked in that large hole in your pic and was still connected to the dash harness connector hidden by the kick panel.
Ditto I recall for my 64 & 65 A's (long ago). I recently was in there on my 65 Chrysler and looks the same, with connector tucked into that big recess. So, need to pull the harness forward more.