I see a few things.
How wide is the bearing shell in relation to the conrod cap?
Is the wrist pin free, or binding up?
If the
oil feed in the crank blocked up, you get a dry bearing that seizes to the crank pin, then the whole bearing spins in the rod.
If the
oil doesn't flow from the bearing due to tight clearances in the fillet radius of the crank pin, you may still have
oil pressure at the bearing but no flow to cool the bearing. No flow is as bad as no pressure.
The conrod shows it has overheated (blueing), and subsequently fractured. It shows the rods aren't up to the task required.
All of this happened in an instant, and could have been from previous high rpm use.
Generally when that sort of failure happens, the camshaft will also be damaged.
Your heads should still be ok, but the valves in the offending cylinder would be bent.
On disassembly of the rest, I would check the rod side clearance on the front 6 cylinders. Once you have the rods out, I'd measure the bearing crush within each rod bore.
I would also look at the good cylinders bearing shell chamfer to crank clearance. Something will pinpoint an assembly clearance issue.