Hi, OvrlndN00b:
First of all, congratulations for your purchase. That is really nice monster and a great base to plan a big tour around the globe.
Now, probably you know it, though, you must be able to cope with all the work that needs to be done, both with brain and with hands, and have enough patience and funds to get to the finish line as properly upgrading and fitting this kind of old pieces of machinery is a quite demanding task.
Just because you asked: forget about rear steering. Period.
The engine is a V8 with double turbo, so you have revs and most of the torque management relies on the gearbox. I personally do not like automatic gearboxes because I cannot fix them, I do not understand them very well, but they can prove to be very pleasant to drive around, even in rough terrain. They are - sorry- they were designed back in those days to last longer than the engine itself so, if this truck has been properly treated and maintained, there should be no problem as long as the truck itself do not fall apart.
About consumption: I assume that you do not worry about that, otherwise you would not have even looked at this truck.
Upgrading the suspension with air things is not an issue if properly done, of course. Maybe you do not even need it.
In my own project, still ongoing, I took a different approach and planned and designed myself the Box or Habitat and contacted a german firm that built the composite panels and made them ship the panels home. It was a decent deal and they delivered timely and the quality of their work was pretty good. I - still- plan to build myself the base-subframe of the Box on a four point torsion free concept.
The possibilities are not that finite, if you think, it all depends on your will, your skills, your hurry and your budget.
Hope you have a great time building this thing and driving it around.
Keep posting progresses.
Pairoa