I installed the Bilstein 5100's a couple weeks ago on my 2020 LT 3.0L and used the 2nd hole and I'm exactly 2" higher, looked like I could of done 2 1/2" but 2" made it level.
You can order just about anything you want, I ordered all kinds of LTZ parts for my LT, all I did was get a VIN from an LTZ and take that number to the dealer parts counter, in your case it might be a little harder finding a Harley GMC to get the VIN.
I have this one on my 2020 3.0L diesel, Autostop Eliminator I've had it on since Feb 2020 never had any problems and the truck has been back to the dealer for warranty work, the tech. never knew it was there.
Mine started a re-gen today couple miles before I pulled up to the drive up window at the CU, when idling the exhaust is louder and the RPM's increase a couple hundred
Here is another option fleceperformance.com/all-lights-on.html small circuit board with a diode. I used pin 10 and 22 referred to boost for which pins to use for different functions.
I bought the GM fog lights from the dealer and installed everything except the jumper wire into the underhood fuse box, took it in today to have it programed and finish the wiring, I lost the sheet with the code, but still had the box they came in (serial number is on the side of the box) the tech was able to call GM help line with the serial number and the help line gave him the code. $131.00