Some thoughts after looking at these pictures. It makes a perfect case for using a by pass oil filter to remove particulate that will continue to circulate right past a full flow filter, without being removed from the oil. All the fine abrasives are going through the engine over, and over, tearing up all the tightly clearanced parts.
Perhaps the engine wasn't properly assembled when it was built, but the damage could have been minimized had the fine abrasives been removed the first pass on the by pass filter. Recirculating for miles and miles did grind up all the wear surfaces within the engine, as evidenced by the pictures.
These pictures also mirror an engine that has a lot of laps in a dirt track car. Fine abrasives enter through the air filter no matter how good the filter is, then work past the rings, and into the oil. If left in the oil, it produces results much like these pictures show. They recirculate over, and over, grinding away the wear surfaces.
If the OP hadn't decided to repair his rear main seal leak, the carnage would have continued, until likely there was a mechanical failure, or he saw evidence that the engine was producing metal filings.
I know, "By pass filters have no place in a hobby car", I heard that somewhere before. But when that one part fails, and starts producing fine grit, unknown to the owner, a better quality filter may at least be able to salvage some of the internals. It may also stave off spinning a bearing, causing catastrophic failure, namely a connecting rod through the block.
The by pass filters I use, have all the removed particulate right at the end of the filter. If there is metal, you'll see it when you change the media, it can't be avoided. If you're not cutting open your oil OEM style filters, you have no idea if there is metal accumulating in the media.
Carry on....
