Reposting - Ok, we now have a better view of the scene of destruction. Overall, very little damage to the most important things.
Alternator stand sheared off cleanly at the base. No debris observed outside or inside the base. The backing plates are trashed.
Elvis and all of his most loyal fins have left the building...
Anybody still alive in there?
And where did all the fins go?
Aha. Cylinders 1 & 2 were hiding quite a few fins. Some surface gouges but nothing serious (1/8" at most).
Oil cooler and cylinders 3 & 4 are fine
Every fin is deformed. They are thick steel so that explains the bang and makes me grateful that the damage was contained by the shroud.
I spotted circular scrape marks on the shroud towards the flywheel side of the engine. It's possible that that it wore one of the fin tabs enough for it to let go and then it took out the rest. Or, it just may have been badly balanced. I didn't see significant amounts of corrosion so my first guess was probably wrong.
Next steps: order a good doghouse shroud, welded/balanced fan, backing plates, alternator, stand and pulley.
Darn, I was THIS close to Pachitto heads...