F250 Fuel tank capacity questions
 

I have a 2006 F250 Crew Cab short bed 2WD 6.0L diesel. My owners manual says the fuel tank capacity is 30.5 gal. I ran the tank dry (yes, I was sitting on the side of the Interstate in Iowa) but was then only able to put 27 gals in the tank, counting the 5 gal the tow truck driver brought. Does anyone know why that is? The tank does not appear dented or damaged from the outside. If I pay $1,300+ to get an replacement tank with 46 gal capacity will I really get all 46?