Hello, basically currently have 8.8 with 3.31 ratio lots of damage from previous owner, new assembly from ford rotor to rotor is 2700, I can get a used one that is 9.75 and 3.73 ratio for around 700. Question is how much of a difference will it make in odometer and if it will match up. Any info is appreciated. 2006 F-150XL 4x2 with 4.2 v6 Automatic.