So I am trying to figure out if my 1978 W-150 came with a catalytic converter from the factory?? I have been trying to sell the truck for 6 months and now I have an interested buyer. He is telling me his "friend" that owns an exhaust shop says the truck came with cats but I am saying that they where not mandatory until 1979. Is there a way that I can conclusively prove to him either way?? I just ran the truck through deq here in Oregon and it passed with flying colors?? So surely if it was an issue they would not have passed it.