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Thanks for picking the Dee-Zee HARDware Series; Double Lid Gull Wing Tool Box. According to Dee-Zee this tool box will fit your 2012 Ford F-150 Lariat w/ 3.5 EcoBoost. To add even more storage to your truck bed you add the Dee-Zee Specialty storage box that fits behind the wheel well, you can find it here http://jo.my/z167nj