I swapped out the stock rear rancho shocks on my '21 LTZ for the 5100's about 1k miles ago and couldn't be happier. It's my first ever pickup truck after many years of minivan or compact car driving and the rear end hop over road irregularities was quite disappointing and a bit unnerving. Thanks for all the info and advice in this thread for pushing me towards the Bilsteins.
I did the rear shocks myself in the driveway, but the fronts will need to be done by a shop. Fronts appear to be out of stock everywhere I have looked, so it may be quite a while before they can get done.
Have any of you left the fronts stock long term and just switched out the rears?