Auxiliary Diesel Tank Gravity Feed vs. Electronic pump

Many years ago I worked in a boat yard with a fiberglass tech . we made fuel tanks for boats . I have since made three diesel tanks for my trucks , all were gravity feed . Two of the trucks had to pass D.O.T inspections for my Jack Rabbit jobs . They probably should not have passed them , but they did . No DOT numbers on the tanks . Ain't nuttin wrong with gravity ,