LoL, AR has nothing to do with the naming convention of the turbo. A T04z rear turbine housing for instance, comes in AR's of .70, .84, 1.00, 1.15, 1.32. The AR is the ratio of the cross sectional area of the turbine nozzle : distance from the centerline of that area to the centre of the turbine wheel.
IE: You can get a .70 AR capable of flowing 200hp, you can get a .70 AR capable of flowing 900hp
Your best bets to learn the limits of various stock bits of peices you have. injectors, pump etc etc, and then size a turbo that will be useful to you, in that power window. High flows are popular.
This LINK will help show you what you can do, with what parts
Thanks