You do not have to do a body lift to get higher than 6" but you do have to add other parts, if you add bilsteins adjustable shocks or procomp adjustable shocks you can go up another 2.75" on top of the 6" lift however you would also require a rear coil spacer to keep from looking nose high.
For example our company vehicle is configured like this
6" procomp stage 1 lift kit
procomp prorunner zx2014 adjustable shocks set to 2.75" in the front
procomp prorunner zx2001 shocks in the rear
ready lift 1.75" rear coil spacer.
for a total of 8" suspension lift.
hope this info help you out, the only reason to use a body lift would be to go bigger than 8" but you can for sure get to 8" without using a body lift.
Discount Auto Performance