To go 6 inches you will need to upgrade the steering or go crossover.Probably need a track bar in the front and maybe new driveshafts.Only place i would buy from is
http://offroaddesign.com/catalog.htm they only deal with our trucks and own a few they are one of us.They sell tuff country springs or their own custom made springs.On the 6 inch lift i would do a shackle flip in the rear which will ride better and gives you a 4 inch lift and use 2 inch left springs so you have 6 inches total.