i know the widest you can get under a ke20 sedan is 7.5" which will fit inside the gaurd, so it can be kept relativly low.
id say wagon would be the same, but also depends on width of diff and correct offset of wheel.
if you have the car jacked up and on stands with the diff still fitted youll be able to measure it up quite easily and get an exact max width and work out which offset ull need to run.
cheers, scott