Hi there: I am looking at changing my 2003 F150 sc s/b 4x4's rear leaf spring to the 7700 series or to the F250. Has any one done this before?? Also what I have found is the the 97 to 99 F250 rear springs as well as the 7700 series fit. What I could use help with is as follows. I am looking for the different spring codes that are located on your driver door jam. It will say SPR then a number and letter. Also along with that I need the last eight digits of your VIN. As there are many different springs, this will help me match the springs with the torsion bars. Not sure if I even need new torsion bars or should I just crank them up??Please send me your codes along with you years and GVW. Thanks