I wish I had a window sticker for mine, but I only still have the bill of sale that just listed "AM radio" and "sunroof" as the only options. I do have an original brochure for the 1971 2.8L Bavaria, and it shows the car without rear headrests. I seem to recall that there were some "1972" Bavarias built with the early E3 (1971 Bavaria) style c-pillar vents and taillights - perhaps it was those early 1972 examples that also had no rear headrests? (I realize this is a trivial, and perhaps moot point, but I tend to get caught up in the details -- old engineer here, emphasis on old).