Like I told you on PM's i ran the spec steel on my spec 3+ and didnt like it. Clutch tore up right away too. I put a spec twin disk with an aluminum flywheel and its much better. Id go aluminum, plus wiht the power you are making you will be fine. There will be chatter with that clutch, but most of it will go away. Once you start making power, there really isnt a clutch that wont chatter or be on/off.
the billet flywheel will cut down on the chatter if not running a twin disk setup, I ran a spec stage 2+ with a cast flywheel running 12.7's.. I went with a promotion clutch and a billet flywheel and dropped to a best of 12.4. I dont know if it was clutch related or not just found it interesting it went faster after the swap
I had a spec stage 3 in my old mustang and in my camaro back when it had a 6 speed, no chatter or problems with either. Mustang made 408rwhp and the camaro made 640rwhp. I ran the stock flywheels back then so no experience with them.
If its a puck style clutch, I would recommend going to a steel flywheel for sure. That puck style clutch will most likely dig itself into your stock nodular iron flywheel on a hard launch and you will end up having to pull the tranny to pry your clutch disc off of the flywheel. The aluminum flywheels dont carry the energy and inertia that a steel one does, which will help with traction but hurt top end. You can get the best of both worlds with a lightened steel flywheel, but they are $$$.