Final answer:
The "final touch" added to the Brown Bomber in the novel "The Watsons Go to Birmingham - 1963" was a hood ornament, which symbolizes family pride and the father's love for the car.
Step-by-step explanation:
The "final touch" that Dad had Rufus and Joey get from the trunk of the Brown Bomber was a hood ornament. In the novel "The Watsons Go to Birmingham - 1963" by Christopher Paul Curtis, the family car, referred to as the Brown Bomber, receives a unique hood ornament from the trunk. This ornament serves as a symbol of pride for the family, especially the father, and adds to the character and personality of their beloved vehicle. Rufus and Joey retrieving the ornament underlines the family's bond and Dad's affection for his car.