interesting thread - check out this site for what the 1966 W111/112 coupe/cab options were:

Special equipment for the Fintails

you can see that the headrests were not yet the "internal" mount - and they were available for front AND rear

these "external" headrests are similar to the optional headrests on Porsche 356's (i know cause i have a 356 with the headrests!)

i rarely see these external headrests

i agree that i would want headrests for safety

i would be willing to forgo the stock look for the safety

also, i have seen 250SE's with the later headrests installed, so it's done

hope this helps

brad in seattle!