W/the 3" body lift and 1.5" spacers you should be able to run as little as a 2" backspacing. SInce you opted for a skinny tire, you should move it as far out as you can to lower your center of gravity. The general rule of thumb is for every 1" you raise the vehicle you need to widen its track width by 1.5". You are looking at raising the rig 7.5"(if starting w/stock height of 28"), so in theory you need to widen the stance by 11.25", or move each tire out about 5.5". Since you are going w/a 9.50 you should consider going w/a 2-2.5" BS rim. Factory BS on IFS is 4.75" so if you go w/a 2" BS rim you will gain 5.5" from the rims themselves. Most of the national tires shops will mount up some different BS rims for you so you can see how they clear.