I absolutely love my SPEC clutch.
I would recommend talking to Josh at
www.chicoraceworks.com in Chico, California.
He is a SPEC dealer and is extremely knowledgable on their clutchs ... both import and domestic.
Tell him JekylandHyde sent you ... he's truly agreat vendor.
What kind of times are you expecting to run with 600 HP? I am aiming for 450 rwhp this winter with the goal of touching 10s.