If you look at the GM accessories Trail Boss kit for non-trail boss trucks, it comes with different CV axles. Last I looked that kit was about $1200 and comes with a warranty ("The greater of either the balance of the vehicle's bumper to bumper warranty or 12 months / 12,000 miles"). Also comes with new dampeners, hardware and a taller emergency jack.
I look at that as GM saying that you need CV axles for anything lift and probably UCAs for anything over the 2 inch trail boss lift.