From the Ford Body builders site:
Frame — Type Ladder Type with Fully Boxed Side Rails and Hydroformed Front Section,
7 Crossmembers, 36,000 psi Steel with 156.5" WB SuperCrew/
163.0" WB SuperCab
49,300 psi Steel with 126.0", 144.5" WB Regular Cab, 144.5" WB
SuperCab/144.5" WB SuperCrew
—...