Im building a 94 Supra NA-t. Whats a good a/r for the turbine housing?
Whats the highest I should go and whats the lowest?

Depends on what you already have to start with. If you haven't got any mods to start this project out, I wouldn't get ahead of yourself yet. If you already have the parts you need I would suggest talking to NA-T.com I believe the site is. They can give you a m,ore accurate idea of turbos than I can. But in order for you to go past 10Ibs. Your most likely going to need a built motor. I only know of one na-t in my area and we talk pretty frequently. He has a small turbo for a supra but a descent size for a na-t. List what you have already and then we'll talk more about it.