Keith,
The problem you describe sounds like a slave cylinder. I had this problem with my Corvette several times. It feels like the clutch is engaged but your foot is not on the clutch pedal. I took the car to GM since it was under warranty twice for the same issue, they claim is debris entering the hydraulics and replaced all of my hydraulics everytime. Makes no sense to me how debris can enter a clsoes system but that's what I was told. Others say it is the fluid being cooked and breaking down since my headers were really close to the clutch hydraulics. I just started bleding the system when I had the problem and it would go away without having to replace anything.
As for clutch I'm using the McLeod RST twin disk. It is supposed to be very street friewndly and holds pleanty of power for my application. TheZguy just sold his barely used RXT twin disk for a good price, too bad you did not snag that one. He said that clutch worked great.