In most BLM lands and National Forests we can spend 14 days in one spot. One person should have 1-2 gallons a day. I would like enough water to drink, make soups, oatmeal, and take solar showers.

14 days of water, at 2.5 gallons per day equals 35 gallons, plus 5 gallons emergency, equals 40 gallons of water, which equals 320 pounds. Yikes!
I really think 40 gallons is too much, but if there is excess I can continue camping.

The plan was to store the water in the bed of the truck, under the shelf by the cab. Not a good plan. Too hard to drag a 40 pounds container out while kneeling.

Putting the gallon containers behind the passenger seat works perfectly. Don’t have to lift them very high to get them out.  Its easy to fill them up in place.  They can be tipped out the door to fill up a 2 gallon container. Three more of these containers, then fill out the rest of the 40 gallons  needed with smaller containers placed strategically.

No need to fill all of the containers all of the time. Camping near a river/lake/stream/pond/waterfall/swamp would reduce the amount of water needed in the truck.
Just have to know where I am going. Ha.