To hold with reasonable pedal effort agree something like a Centerforce. I would suggest call Silver Sport who bought Keisler. They have a twin disc clutch they recommend for high HP/torque applications.

I run a Keisler behind a warm BB stroker. The highest rated version (600 ft lb torque rating I believe). It has done OK even though my engine made 687 ft lb on a dyno after freshen and tuneup. With this transmission shifting as you approach and exceed 6,000 RPM can be tough.

I think it is worth getting the right clutch and give it a try. Later on you can upgrade to a Viper based 6 speed if you want.