Any thoughts on how much it'd cost to restore this rig?

I would suggest getting a 4x4 pick up truck and a truck camper. It will do all that you have mentioned.
That old 460 motor will kill you on fuel too.if you want the fun of a build? Bu a old Fed Ex truck or Bread Truck ,they will have been fleet serviced their whole lives,you have a aluminum body and great diesel to get you there,many have Allison tyranny’s too.