I just called Zone to clear this up.
The 4" and 6" lift definitely have the same size
strut spacer (same part # 02267b).
The only difference between the 4" lift and 6" lift is that the 6" comes with a
preload spacer.
Guess that puts Superlift back on par with Zone
Also. It is true that they will give you the 5.5-6 inch of lift without the bils installed. But once you get the bils, you discard the preload spacer, so now you're back to 4". So there is no additional lift on top of the 6". For the 4", as stated before.. there is no preload spacer, and the bils are to be set at zero. So you can have additional lift with bils on that one.
In other words, to upgrade from a 4" lift to a 6" (with bils).. you just set the bils at 2.8, get the 5" rear springs, and an alignment. The extra $100 for a 6" lift is them charging for the preload spacers.