I've got the 2 knobber in my '13 LT and wondered if anyone has ever swapped that and the dash cover for the touchscreen from another?
I'd imagine and guess they only used 1 wiring harness because that'd be cheaper and simpler to not use several wires in a big connector than to stock and SKU 4,3 or even 2 different wiring harnesses. So that should simplify wiring, but I know the openings are different, etc.
It may cause an issue with the Onstar, etc but I'd try and iron that out.
Just haven't found anything from searching yet about upgrading to the better OEM stereo besides an aftermarket head unit.