i think the cummins have higher output alts anyways. i may be mistaken but im pretty sure they do. it may not be by much tho but i remember reading it somewhere. if anything the high output alt would be for the intake heater grid thats only when its like below 50 degrees tho. i think they can draw over 100 amps. plus your fuel system will also draw power too. so the high output alt from the factory seems like it might be true.