I'm baffled by the thought of a seized /6. I know they'll stop if they get hot, but let them cool off and they'll usually restart. My in-laws killed one in a Volare after they didn't change or check the oil for 18 months or so, but the only reason it wouldn't start was #6 rod escaped and broke the starter off of the bellhousing...
Looks like a great buy at that price.
I am betting it ran out of oil or water........or both!
Used to be my weekly driver between grand island and York, engine seized on the freeway and I coasted off an exit and got it towed home.