R/Joe, thanks for the forum, this is extremely comprehensive on more than just horns! I was not aware of the different mounting point on models, but understood that power steering influences angle of the horns.
So were the mounting points different on each model? Does anyone have photos of this?
I also learnt that you can adjust the tone of your horn by turning the screw (under the sealing wax) on the back of the horn. Also different frequencies for different models.
It also appears that all models had two horns.
This may be old news for the long term owners but there is a science behind every aspect of the car.