Well it sounds like the motor is in good nick, but for 4wd purposes, you want a good air filter setup. Cyclonic if you can. Like what is in the cruisers or the MQ patrols (diesels)

The gearbox and axles seem a bit pansy to me, but only bieng pushed by a 4 cyclinder, I wouldnt imagine they would break much. We got a lot of slop in the rear diff early on, though it didnt ever break. Possiblly the uni joints, but we never bothered to fix it. My dads idea is that when it breaks you fix it.

Watch for rust in the body mounts to the chassis, particulay the front most ones. Ours showed heavy rust there. It must be a water catch point. The bottom of the doors showed rust, but that is common in 4wds when the drain holes fill with dirt and collect water.
They seem to be lightweight and get blown about a fair bit on the highway in any sort of crosswind, but just drive to conditions and you shouldbe fine. Uours was a single cab, so not sure on the room that the king cab gives.

OPurs gave us plenty of clearence for our purposes, and as the joeybox is not hanging down, it doesent seem to catch much, which is a good thing. Cant remember if it is a married or unmarried joey box, but if you keep it original then that doesent matter.

Hope that helps. Anymore questions ask away.