My guess is at least $5K for the Z51 package. I'm only interested in drag racing so most of the items it offers I don't need or want. Sure don't want the larger wheels/tires. That could only add weight. Don't need the cooling, dry sump or larger front rotor for drag racing. That larger front rotor would make fitting a skinny that much harder. What I would need is a lower gear offering for the automatic tranny.
Not sure what the electronic controlled differential does for us vs. a standard limited differential but I would think again only for ring type racing.
I'll stick with the base and go from there to build the car I want.