I'm considering my options before buying a tool box for my 05 F350 CC SWB 4x4 when it gets here. Has anybody run across a box that goes over the wheel well and extends both to the cab and tailgate and sits below the rail. I'll be pulling a 5th wheel so a rail mount won't do. I could just buy 2 of the half length boxes but don't want to do that. I don't even know if anyone makes um or if their even practical, just exploring all options.