I'd look at either:
http://www.advancedclutch.com/v3/app...tail.asp?ID=31 (HD-SS) (good for 245lbs of torque, 55% harder than stock to push down)
or for a stronger clutch but still reasonably streetable....
http://www.advancedclutch.com/v3/app...tail.asp?ID=32 (HD-R4) (good for 311lbs of torque, 55% harder than stock to push down)