Rare? Yes, relative to the ease of finding a cast-iron slant-6, the aluminum engines are rare. But there are considerably rarer engines, too.
"Rebuildable core" means more with an aluminum slant-6 than it means with an iron one, too. It means an engine that has no significant corrosion in the water jackets or crankcase, has no cracked or otherwise damaged cylinders, and either turns over or can be freed up without destruction. According to the answer to my question, the one under discussion almost certainly does not qualify as "rebuildable" any more.
