Ok so a few things... The bottom rear bolt going from the block to tranny was missing. Both a spring from the clutch disk was missing and the clip for the pressure plate cover was loose and floating around. Here's the million dollar question: Could the missing tranny bolt cause the carnage when all others were torqued to spec... or chicken/egg scenario (did the spring fyling out cause the ring to pop out or vice versa)?

Also keep in mind this happened under braking, not accelerating.

Clutch disk is from Tampa Clutch Supply, and they rate it for over 500hp (which I'm nowhere close to). My first disk from them completely bowled.

As far as dowels... both tubular dowels (bottom back, and bottom front to starter) are still there.