By unexpected popular request I'm uploading the parts I created for installing an Alpine iLX-702D 7" touch screen head unit in my Land Rover Discovery 2.
These are the parts I used to adapt the Discovery 2 dashboard to fit the head unit and to finish it off. These should also work for a 1995-onwards Discovery 1 and may even fit a soft dash (late model) Range Rover Classic.
Firstly we have a block that supports the single-DIN cage. As the top rail of the dash has to be trimmed to fit the large screen, there is now nothing to stop the cage from moving upwards if you hit a bump. This could cause it to tilt or rattle. This block pushes in from behind the screen, wedged between the remainder of the top dash rail and the cage and provides support. In my case it's held in by friction as it's a tight fit. If you aren't concerned about cosmetics, this block could just be made of wood and you don't need to worry about the other two parts.
Secondly, we have a piece that fits below the screen from the front. This does help to support the screen and prevent it from leaning forward under its own weight, but is mostly cosmetic. It has two recesses for the screws that hold the plastic dash to the metal bracket inside. Having these hidden is a nice extra security feature.
Finally we have the top cover. The head unit is pretty ugly without it but this isn't essential. It sits over the top of the screen and is held in place by small magnets, this works as the back case of the screen is steel. The lower edges are shaped to fit the contour of the top rail of the dash as closely as I could. After sanding smooth, I painted this part along with the lower support piece with matt black paint to match the trim supplied with the head unit.