Those 4.9L engines are too reliable, but this one has been abused to long. Sounds like time to rebuild or replace. With all this sludge inside don't think Choelesterol medicine is going to repair it. Has to be an excessive amount of blow by. Time for major surgery.

 

Replacing the oil with deisel is kind of a scary idea to me, but I'll try it. I'm starting to think Bill Witshire is right though.