I called FR parts dept and ordered directly from them. No dealer involved. 1 574-642-2640 - ask for Cathy, she is great help at deciphering what is needed. I believe this was called a c-channel rail....I told her I wanted the same rail parts as my exterior grill attaches onto ....you'll just need to tell her what length you want.
2012 FR Flagstaff T12SDTH
1996 Shadowcruiser Pop Up Truck Camper
1967 Newell Motorcoach
2003 Ford F150 5.4 V8 Triton Super Cab
2004 Nissan Titan LE 5.6 V8 4x4 Crew Cab