Just get the OME HD springs/shocks. It will sag down to a 1 - 1 1/2" lift in a year or two. They arguably give the best ride for Discoveries.

 

There are no springs currently offered that will give you only factory specs. height other then some Quote HD rover springs and they collaps very quickly to and modification or off roading.
ARB coils are OME's.
All H.D. coils will give you a lift, some more then others, usually not more then an inch over your trucks original height, but even that will raise you 2"plus from it's current sag.
AK, Let's talk this weekend.
Mike