Those are the shock units for the rear bumper.
2511 was originally a chrome bumper car, but had the later impact bumpers installed when purchased by me. An old timer owner once told me that when the newer model Pantera arrived some owners of the earlier cars did not want to be driving the "old" version and converted to the L model bumpers.
Of course many owners now remove the later bumpers in favor of the small chrome versions.
Just another example of adding your personal touches to suit yourself.