Best Air Shocks for Raising Back end?

You may have heard this before (or not) New springs, For better handling & control.
Longer shackles if you want height. Then you can remove them later if you want.
Springs carry the weight of the car spread out over 4 mounting points approx 4’ wide X 5’ long.
Lifting the car with shocks carries the weight of the car on 2 points about 18” apart on a Sheetmetal brace not meant for those loads. A shocks job is to control the movement of the spring only.
Coil-overs are usually mounted to places designed for that stress.