W116 rear headrests - YouTube

Seat posts are in better condition than expected, but as expected I don't have any hardware in perfect shape. Video shows condition as well as assembly overview. I can provide more pictures or detailed video as needed.

As a side note the plastic triangular piece and small spring are actually completely unnecessary if you don't care about pulling the rear headrests out without removing the rear seat frame. I have pulled at least one set of these that did not include them - once the seat frame is out you use a screwdriver to press the release button instead.

But as for what I'll sell it'll be a complete kit that includes everything but the plastic trim pieces for the seat skin.