There are Australian Design Regulations (ADR) limits to tyre sizes. If I recall, the limit might be 50mm over the vehicle's designated tyre size defined on the tyre placard or in the owners' manual.
That means you can probably get 315s on it legally, but may need to change the offset of the rims to do it. The offset can be changed by a small amount without engineer's inspection (I think that limit is 20mm) but there will be issues with inner guards and trying to reach full lock or full suspension travel.
Beyond those limits, the vehicle must have an engineer's certificate relating to those changes.