1)a dealer is selling a ford f-550, he says the gvw is 13,500 is that right? i thought the gvw on a 550 was 19500, 450 17500,and 350 13500. whats going on??? 2) is a 3126b cat the same as a c7? im looking at a f650 that has the 3126b paired to a auto is that a good powertrain? the cat is better for pulling then the cummins right?