[WB72]

I am new to air suspension.
After reviewing many posts, I am still confused about the height of different air bag setups. What is the amount of drop, ride height, for the following set ups?

1.) Just replace springs with air bags with trailing arm rear suspension?
2.) is there any need to use of drop spindle? Or A arm?
3.) how big of a step notch is needed to lay frame?

Also, what are the basics that need to be done to lay frame? I am thinking I want to do this with this next project, and want to know what I am getting into.