[mrvedit]

As an update to my post #24, my wife did not want the Corbeau seats for daily driving but still wanted to be able to use 4-point belts at the track.
I therefore bought the entire interior from a wrecked 2015 335i (F30) which have the separate head rests to support racing belts. The seats and all electrical connectors fit and worked perfectly, although the local dealer had to re-code the airbag computer to accept these seats.