This clutch is a match made in heaven!  The awesome (and great value) Blackbone 9500rpm spring combined with the UFC ultra HD steel shoes (heavier than FS for more force and wider for more grip).
 
This combination of spring/shoes results in a circa 8750rpm, very strong biting point.  
 
Works extremely well on large small block engines and small big block engines.
 
Comes as photo, with hardware