I have a 08 F250 ext cab 5.4 FX4 with 3.73 gears and I'm looking to go with 4.10s. I have factory 20 rims and trying to see if switching will help. I'm looking for more off the line giddy up I only use mine for towing my trailer and car about 5500 to 6000lb. I AM currently looking at a 08 with 6.4 but I only owe around 13k on mine or 23 payments and have 60k miles on it so not sure if going to psd is worth it. Right now distance to the race tracks are one is 50 miles and other is about 30. I get 9.5 towing now. What do u think?