I saw most of the pictures a few weeks ago. I asked him to check the intake gasket to see if it had been compromised at all.
However, you normally don't get
oil way up into the intake plenum like that unless it's a bad PCV or something similar.
The only other way
oil ends up going backwards like that is if a loss of ring seal has occurred. Then you get
oil on the cylinders combined with reversion from the cam and it pushes the oil up into the intake tract.
Valve seal wear or valve guide wear could have contributed to it, but I would look to see how much crosshatch is left on the cylinders. If a lot of the cylinder looks shiny without crosshatch, I would look toward an overly rich carburetor condition, which would wash the oil off the cylinders and then you'd lose ring seal.
Also, you can't bet on it 100% of the time, but if you pull all the pistons out and a lot of the top rings are very near each other or the gaps lined up, it's often a sign of detonation.
Could be a multiple of issues in a perfect storm....oil consumption due to bad valve seals, leading to some stuck rings, then pushing oil back up into the intake tract, etc.