Well, our latest failure looks to be a de-lamination of a main bearing. Bearing cavitation has been an issue in the past, and we have 2 units that haven't been "upgraded" with the later style, fully grooved, main bearings. We haven't gotten all the bearings inspected, yet, so I am not sure if we have any damage to the crank.
For all of these engines, the best thing I can say is be sure to get all the service bulletins currently in effect, and try to get all previous service bulletins. These will sometimes tell an interesting story if you can go back and see all the various "fixes" for a given problem. Exhaust, oil and coolant leaks are a problem.
On the 8-cylinder engines, they had a lot of vibration problems in the past, and aftercooler mounting problems. Could be related. I do not know if any of them had the same con rod problem. Some folks in Michigan had a broken crank that was caused by "lack of oil" or similar story. Be sure to check all the internal oil lines as Mr. dwedel can attest to.
Operationally, we have trouble keeping the air/fuel control system calibrated. Our exhaust oxygen sensors are subject to various contaminates, though. Basically, we have an extremely high amount of maintenance to do just to keep up, never mind trying to make improvements. Resources are too thin here.