[blykins]

My typical Cobra package for the small blocks includes a RAM HDX, Powergrip, or Powergrip HD clutch kit. None of the above have a "heavy leg" pressure plate. The HDX clutch is rated for 450hp, the Powergrip is rated for 550hp and the HD is rated for 650. These are all 10.5" diaphragm pressure plates and are available for most input shaft sizes.

I'm curious to hear what your previous combination was. If it was a stock T5, then it really doesn't matter which clutch you were using, they don't last long behind most high horsepower engines.