Yup, Z71 only gets ya decals,shocks & skidplates. G80 was an option and as far as the gears, GU6 for 3.42 and GT4 for 3.73, I'd say it's about a 50/50 mix.
As for the newer Z71s, not sure about what year it started, however now you don't automatically get 4wd when you get a Z71.