Last known p/n for the factory style GM air shock was 22046433 for LH and 22046434 for RH. Everything in that system was sold by the piece darn near. The fill valve, the air lines, air line clips, etc. The 504-564 appears to be a kit (look like Gabriel hijackers to me, but I'm not sure) and will probably suffice, but they're not like the factory style, unless you don't care about that. Air lines cannot be reused since the Delco kit has screw on connectors while the original stuff was push on/clip on.
JMO, the leaning isn't likely from the shocks. 99% of the time in my experience, leaning is caused by a weak spring or in the extreme, something is bent that shouldn't be. Think about it. If you took the shocks off, the car would still be held up by the spring. The shocks only dampen bumps and rebounds.
It's also likely the air pressure for shock wouldn't be at fault for the lean because they share the air pressure and self equalize.Unless there's something in the air line to one of the shocks that's clogging it- extremely zero to miniscule chance of that, however. If the shocks are still good on the original, air leaks on the original systems are normally due to the tiny little double O-rings on the air lines drying/cracking. Replacing those usually helps.
It's a good idea to ensure that your factory air shocks maintain a minimum of 25 psig. The delco replacement kit also recommends minimum of 25 psig. IMO, it sorta sucks because at least with the factory air shocks, the car sits up a bit in the back even with the minimum.
Just some things to consider.