Thanks, Mike. You are close, yet not entirely correct.
The headrests were in fact available as early as October ’68. As was the black rear view mirror. The door mirror I mentioned (which you cannot see in the photo) would also be a clue do date the car as a ’68 model… or later.
And as you now may gather, the model year of this particular car is 1968.
Take heart though; you were right about the Nardi wheel
I use the car as a daily driver from April through October (if the weather permits), and I much prefer the Nardi wheel to the original plastic one (this particular car came with an ivory coloured wheel, which I have carefully stored). Not just because of the looks, but also the improved grip and the fact that I find the steering a little more involving - the smaller wheel does not reduce the number of turns lock-to-lock, but it changes the distance your hand moves while doing this.
I do have the 16” Nardi though, not the 15”. This is a little closer in size to the original steering wheel (17”?), and it does not block the view of the speedo/tacho as much. A matter of personal preference, I guess. As for being counted as an error; very easy to amend if need be.
Halogen headlights were announced sometime in ’68, though not actually available before a year or two later. As for the actual bulbs in place now, I'd take whatever provides the best light (this being a daily driver throughout parts of the year)..