Motor Trend say 2004 F150's Frame is 9 times strongs than previous F150. Ford say in 2009, they has increase 10% more strength. So, that means from 2009, F150 is 10 times stronger than 2003 F150
"The new frame is boxed and partially hydroformed, features seven crossmembers, and is reportedly nine times stronger than the previous F-150's. "
Read more: http://www.motortrend.com/roadtests/pickup/163_0308_2004_ford_f_150/engine.html