I wish I had the definitive answer but I can only give my best advice based on experience with plants of all kind, including potted citrus. First I would water the tree well for a couple of days with a soaker hose. While soaking the roots, dig the hole at the new home. Wait a day to give the tree roots enough time to pull up the water and so the soil is very damp but not soggy. As the CES agent who wrote a weekly gardening column in the Sunday paper used to say, dig a $10 hole for a $1 plant. Add any amendments to the excavated soil before planting. Next dig the tree with as much soil around it as possible. I think the minimum safe root ball will be 4-5 feet wide, 3 feet deep and bigger is better. It may take 3 or 4 people to pick it up. Wrap the roots, plastic is OK for just a couple of hours, if longer you need cloth fabric such as burlap. Plan on making a special trip to the new home with enough people to unload and plant immediately. Back fill the hole and water, water, water. You may want to use SuperThrive or a root stimulant right after planting. Good luck. Contact your Arizona ag school cooperative extension center in your county and ask their advice. The earlier you get it moved before HOT summer sets in, the better your chances of survival,

All that is good advice, but some is not practical. It's a half-ton root ball if you can hold all the soil on the roots.

You simply would be astounded at the fat woody "sticks" with some stubby thick roots that were planted commercially in Florida groves a third century or more ago, so citrus must be pretty tough.

If it were me, I'd get as big of a root ball out, as suggested, but not try to keep any soil on the roots. Personally, I'd hose them clean to reduce weight and to get them soaked. Before I dug at all I'd trim and thin out at least half (preferably more) of the foliage, to reduce water demand later, preferably thinning evenly to keep sun off the bark.

In transporting, I'd keep a soggy blanket over and all round the roots and a soggy sheet over the whole plant. No plastic to trap heat unless totally shaded (inside a reasonably cool truck) or unless covered on top with cloth, preferably light colored and preferably wet (if in sun).