I replaced in-line fuel filter,did't solve problem.where is oxygen censor locate

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the truck started shutting off ,like it was'nt getting fuel,so i replaced fuel in-line filter,worked one day ,then started spitting & idling irratic & shuts off,so i'm trying to locate problem,is it the fuel pump or maybe the oxygen censor & where are they located? need advice asap please, thank you,it has a 454 engine and is a 4 door dually.