Have you tried Googling the complete VIN possibilities w/ Coupe and Roadster viariations added to the stamped sequential six?.
If no results get the two VIN possibiles posted here or somewhere online so if the car exists and someone searches their Vin they may find it!.
If the car can't be found, the block's probably worth most to a '66 L72 'Vette guy that needs a motor and would prefer an original casting/suffix correct block in his car and doesn't want to play the restamped 'restoration motor' game..
~ Pete
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I like real cars best...especially the REAL real ones!