A standard 2004 Dodge Ram 1500 gas tank can store up to 26 gallons. On some Ram models, the tank can be upgraded to allow up to 35 gallons.
The 2004 Dodge Ram has three potential fuel tank sizes, which depend on the specific model of the truck. The default model is 26 gallons, while the ST and SLT Pickup have 35 gallons.
The tank on the latest Dodge Ram can be upgraded as long as it is not the SRT-10 model, according to Cars.com. The ST, the SLT and the Laramie are all models that can come with a 35-gallon tank as an option.