The factory measurements, if my memory is correct are 17.5" for the front and 17" for the rear, taken from the centre of the wheel hub to the bottom of the wheel arch flare.
These are for the petrol models; I think the diesel is an inch higher at the rear due to the heavier duty springs.
I've got HD springs on mine and 1.75" shackles and it sits about 2 inches higher than standard.
Hope this helps.