Variants of a mold are catalogued separately, so each one has its own sets and minifigs. Check these too if something you expect is missing here.

• 6584 Vehicle Base, Train 6 x 24 with Two 1 x 2 Cutouts and 3 Round Holes Each End Alternate of this part
• 92088 Vehicle Base, Train 6 x 24 with Two 2 x 2 Openings and 3 Round Holes Each End, Reinforced on Bottom Side Alternate of this part