Difference Between Air/Land Launched Missiles

Provided that we have got two different missiles by name(A & B) but yet they have in common the guidance system as well as the engine say a turbofan; can they be called a single missile having two versions i.e air launched & land launched?? If not does this mean that though both have turbofans but thrust profiles/specific impulses are different for air & land launched missiles?? I do know that there will be some aerodynamic differences but what about internal makeup??