Sounds like a low oil pressure condition caused the failure. Could be several causes. Low oil level is one, failed oil pump or broken oil pump driveshaft is one, or several other causes. It doesn't take very long, especially at higher RPM under load, to smoke a main bearing to the point of failure where the crank locks up.
Assuming the cause is oil level, and not an oil pump failure, which is rare after that many hours, and your bilge wasn't full of oil when you checked it after the first noise, the oil must have gone out the exhaust. Could have been a hole in a piston, or maybe a broken ring land.
As for the piston pin, not sure if they use floating pins on the 343, but pressed pins are pretty common on older V8s.
In any case, glad you got it fixed!