kbuskill
***CAUTION*** I do my own stunts!
If you decide to keep the stock height, in my opinion you can't go wrong with the factory system. Rockauto has the OEM z55 autoride rear air shocks for $250 each. I just installed a fresh set in each of our Denali's and they're holding pressure great. Originals on my '12 lasted 117K and were holding pressure fine, but one started to leak a little hydraulic fluid so I replaced them. The units on my '07 were unknown and were leaking just enough air to require replacement. Both will hold pressure 100% now with a 4000' trailer.
Arnott will buy your old factory auto ride shocks for cores and rebuild them... at least they would a few years back when I swapped mine... you should call and ask them. They sent me shipping labels and everything... may recoup some of your money.