I had those white seals replaced, too, along with new bed doors. The seal comes in a roll so my dealer cut pieces long enough to go around the entire perimeter of the doors (top and both sides) and installed it so there is no exposed cut end at the top corners.
2011 Rockwood Signature Ultra Lite 8293SS, 12K Equal-i-zer
2016 Ford F-250 XLT SuperCrew, 6.2L, 4x4, 6'9" bed, 3.73
2010 Rockwood Roo 23SS (2012 - 2014)
2009 Ford F-150 XLT SuperCrew, 5.4L, 4x4, 5'6" bed (2012 - 2016)