Hey if you're planning to put an aftermarket clutch...you will definitely need to change the flywheel. The stock dual mass flywheel will only work with the stock altezza clutch. I recently had to change my clutch and I got an incredible deal on a trd lightweight flywheel and exedy organic clutch kit (clutch disk...pressure plate (clutch cover) and release bearing from www.B-spex.com
... they're very helpful. Note that you will need 8 genuine toyota flywheel bolts in order to install the flywheel. This set up is as smooth as the stock clutch and will give you added engine response with the lightweight flywheel.
If not, message xnickx, he can definitely hook you up with the stock clutch/flywheel. Anything stock...chek out xnickx!
Good Luck with your clutch woes!