UPDATE
I got the water system installed. It consists of a 20 gallon water tank, a 12v water pump, a water purification filter, an indoor faucet and an outdoor shower.
I started by removing the storage boxes I had built behind the driver's seat and re purposing the steel framing to build a mount for the water tank.
The mounting bracket is bolted to the floor of the truck cab with the bolts that previously held the rear seat and seatbelt. The tank is held in place with 3 ratchet straps.
It is a sump tank, so the water drains out through the bottom of the tank. This lets us get all the water out of the tank if we need to. Under the tank is a 40 micron spin down filter. This removes sediment that could harm the pump and quickly clog the finer filter elements. The water pump is also mounted under the tank. It is a 12 volt, 3gpm, on demand water pump with a 50psi shut off. It is powered off the house battery and also has a manual power switch mounted under the tank bracket.
From the pump a hose runs along the frame rail to the rear bumper, where I mounted a quick disconnect hose bib and ball valve. This will be used for outdoor showers or rinsing gear.
There is also a hose that runs into the camper under the passenger side cabinet. This is where I mounted my water purification filters. I bought 2 filter housings from ClearSource RV and the replacement filter pack for their Nomad water filter system. Then put the housings together with stainless plumbing fittings and installed the filters. The water runs through a 5 micron, then a .02 micron filter. According to ClearSource RV this will remove bacteria, parasites, and viruses.
This filtered water comes out the faucet. It will be used for drinking water and doing dishes.
Water that drains out of the sink will flow into a 5 gallon gray water tank directly below the sink. This tank can easily be disconnected from the drain hose and walked away from the camper to be dumped out.
Here is the video for more detail