The D2 is a better looking vehicle -- it just is. And, the LR3 and beyond are more Palo Alto cruisers than off-road machines. If you invest in a new short block, rebuild your heads and refresh all of the wear items in the engine bay your D2 will be ready for a reliable 100K miles of service. Bake in the suspension mods you are looking at (assuming driveshafts would be included) and I can't see what would be a continuing area of concern for reliability since you'll have touched the known trouble spots. Only other area would be the brakes which are easy and relatively cheap to bring up to snuff.

 

The LR3 is a more capable off road machine than the D2. The $3K I suggested would be enough to get the air suspension, front bushings, and cooling system straight with some leftover for tires(if you do the or yourself).

Rods are the easiest way to lift the truck. I run 285/60/18s on my 3 and they look tough enough and don't require a lift.

 

One problem you may not have thought about is that the car may sit for a while totally unattended as your son might get deployed on very short notice. We all know rovers get very unhappy if they are left by themselves for a while, but mice really find that hollow on the top in the plenum an ideal spot to camp out.
I left a Volkswagen GTI all by itself when I deployed on short notice. It was not happy with me despite being in a storage unit.

 

Yep, been there and done that. I plan on helping him out if/when this happens and probably get the truck somehow to my house.

 

Buy him a 100 Series Land Cruiser. Nah drop the 18K in the Rover. Actually the 100 series are very capable and reliable. I have a 99 D2 that I love and also a 2002 LX470 with AHC so I have a lift when needed. It's really up to him I guess. Show him some Land Cruisers outfitted he may like them.