OK guys needs some info. I have a 2000 4x4 expy getting ready to get the fabtech 6" lift on it. Want to get me some nice rims and go with BFG tires. 1. What is back spacing on a rim and what does it have to do with the wheel? 2. What is the real difference between the 9.75 and 10 inch rims? Any information to help my understanding would be most appreciated.