a 833 od shifting issues
I had a chance to closely examine the failed clutch.
The three fingers that disengage the pressure plate are suspended from the outer housing and have a large adjustment nut to set the finger height. This piece has a cross hole where a pin passes through for the finger to pivot on.
Based on the two stages of failure; initial hard shifting into reverse and first then no release at all of the clutch after a poping sound I believe the inital failure was the piece that the finger mounts on cracked through where the cross pin is. This prevented that finger from providing its full range of motion and the resulting drag that made shifting into reverse difficult. The pop sound I heard was the pivot piece fracturing at the threads into the adjustment nut resulting in no pressure plate disengagement from that finger.
The new clutch is the same three finger style but is a performance version rated for up to 500 HP engines where the one that failed was an OE replacement. The piece the finger pivots on and its threaded adjust area is much larger in diameter than the OE clutch. FWIW, the failed clutch was a ZOOM OE replacement assembly the new clutch is a RAM "Muscle Car" high performance clutch.