Well you didn't ask me specifically, but if you want to run chains on all six you are going to have to go with 1400.20 or smaller tires. There is just no way to run chains on the rears of the five ton with 1600.20 tires.
As for buying chains, Laclede in Hillsboro Oregon makes great custom chains to fit anything you want. As for being in Arizona, go to the nearest tire shop that does big trucks, logging, and farm tires.
Tell them you want a set of Road Grader Chains made up, and to double up the cross bars. What i mean by that is you want fairly close spacing on the chains that go across the tire.
Figure about 325-350 per wheel but you will get good heavy duty chains that are made for a big truck.