What is a good installed price for a 6" to 8" suspension lift, 37"x13.5" tires, and 20" wheels that are wide enough for the tires? This is for a 2010 F-250 PSD 4x4. I was talking to my dealer about it the other day when I was there and they quotes me at about $6,500 for any 6". I would like to have them do it because they guarantee that it won't void my warrantee if they do it, but they can't completely guarantee that it won't if I or someone else does it. Just not sure if that price is a fair one or not.