To add something else to this topic-
Here is my 65 Caprice with the factory installed "LevelAir" system.
The vacuum powered compressor is mounted on the drivers inner fender,with rubber hoses going to hard lines run along the frame rails to the rear,where a valve is mounted on the rear control arm.When weight is added to the car,the valve sends air to the shocks,keeping the car at the same height.It's fully automatic-no controls.
It gets vacuum from the carb and clean air from the breather filter.
Mike.