The present disclosure relates to hull conversion of existing vessel for tank integration to allow storage of multiple hydrocarbon and non-hydrocarbon products onboard the existing vessel. In a converted vessel, a first liquefied hydrocarbon fluid may be stored in an added independent tank, while a second hydrocarbon fluid or a non-hydrocarbon fluid may be stored in an unconverted cargo tank, which can be any one of a centre cargo tank, a port side tank or a starboard side tank.