How much HP and TQ is the stock clutch rated for on an 09 Mustang GT?

With my current mods I'm putting out 350ish HP and 360ish TQ at the flywheel. That's based on Dyno #'s to the rear wheel of 308 HP and 322 TQ. I'm getting ready to start another round of mods which will push it into the low 400's HP and high 300's TQ. It will remain N/A and I have no future plans to run forced induction. I'm considering either a SPEC Stage 1 or possibly a Stage 2 clutch and flywheel. Someone told me they thought the stock clutch was similar to a Stage 1 and could probably handle the extra power. I find that hard to believe, but if true it would save me some bucks. I would only go to Stage 2 if absolutely necessary due to the difference in driveabilty.