Yes you can, I have my 150 gal hooked up that way. You have a few options for the hookup, but your basic supplies are 3/8" diesel rated fuel line, 5/16" diesel rated fuel line, 12+ hose clamps, fuel selector valve, SPDT switch, wire and a inline screen.
WARNING: The screen is extremely important to protect the valve. Otherwise, you may end up like me where a small piece of plastic finds its way into the valve, jamming it so fuel is drawn from one tank and sent to the other causing a overflow and visible trail showing where you have been.
The stock setup has a feed and return line, so you either need a 6 port valve or two 3 port valves. If you have an Air Dog or FASS, you will need one additional valve.
The simplest setup would be with a non serviceable valve like a 6 port Pollak
. The Pollak valve is somewhat inexpensive, has the ability to switch the wire for the sending unit automatically and stays in the last position when power is removed. The disadvantage is you can't take it apart if it gets jammed.
Another option would be a serviceable valve like this 6 port Greasecar
unit. It is spring loaded so it will return to its default position when voltage is removed and it can be dissembled to remove debris should it get clogged. Disadvantages is EXPENSIVE, dose not switch the sender, so you will need a little extra wire.
The basic setup is to cut out a few inches of the feed and return line on the DS frame rail. Insert valve in between cut, plumb in aux tank. Intersect the yellow/white wire for the sender. Mount switch in cab and supply 12v and ground.
Note: if you switch tanks while the truck is running, it can take about 20 min for the gauge to move from Empty to Full.