John,
Were "left over" engine assemblies from production "recycled back to service replacement complete engine assemblies" after production ended?
Normally, any "leftover" production engine assemblies were returned to the engine plants to be converted to the next model year's specs, then returned to the assembly plants for production use. Complete engine assemblies (intake to pan) were only available while those engines were in active production, and weren't shown in the parts books. Besides just component parts, normally the only engines listed in the parts books were short blocks ("partial engines") and fitted blocks (just the block, pistons and rings).