Assuming it's a 1500, it depends on how your truck is configured. For the Big Horn, the standard tank size for the QC is 26 gallons. Standard tank size for the CC with long bed is also 26 gallons. Standard tank size for the CC with a short bed can be either 23 or 26 gallons, depending on how it's equipped. If you post your truck configuration we can tell you which size tank to expect.
The fact that so many are equipped with a 23 gallon tank is ridiculous to me, especially since the upgrade from the 23 to the 26 gallon tank is a free upgrade.