The widest I'd recommend on a 9.0 wheel, for safety and handling reasons, is a 295 tire. Even the factory 275 tires are actually a little on the wide side for a 9.0 wheel, they should have used a 9.5 wheel to be perfect.
Will the 315 fit? Sure it can be put on the wheel, but that tire was designed to work safely with a 10.5-12.5 wheel. If you aren't worried about handling, or overworking the sidewalls, or wearing out the middle of your tread pattern...by all means do the 315
