If I want my X to put down 350 HP to the wheels, I understand that torque will be close to that as well. Other than a clutch kit (clutch and pressure plate) that is rated for that torque, what other driveline/transmission components do I need to worry about upgrading?

I'm currently planning to upgrade to an Exedy Stage 1 (or Stage 1 HD) clutch kit.

 

A search probably would've answer this but I am feeling generous today.

None...stock trans/drivetrain is fine.

You might want some bushings and a shifter kit to clean up the feel but power wise, 350whp is nothing.

Many of us have ran upwards of 600wtq on stock tranny and no ill effects yet.