Regardless of what the fuel tank size is supposed to be, I wanted to know how much fuel they actually hold. I also have a crewcab long wheel base truck, so this might be of interest to the original poster:
When run completely dry, the front tank will hold 22 gallons when filled to the top of the filler neck. The rear tank will hold 21 gallons. I've run both tanks dry intentionally at different times to find this out.
I've also determined that when on the freeway, once the needle on the fuel gauge touches the red on the gauge, you can drive an additional 60 miles before the tank truly runs dry. Once the truck starts to sputter from lack of fuel, it only takes 3-5 seconds for the other tank to kick in once the switch is flipped.