Most of the older fords have a metal filter screwed right into the carb. It almost looks like part of the carb. It should be at the end of the supply line from the tank. Someone may have also added an inline filter somewhere or removed it too. On later trucks they are along the inside of the frame rail on the drivers side. Follow your line from the carb back and see where it goes and if anything is along the way. If not add one!