Apparently that VIN number tells me it is a Chevrolet Corvette with a V8, two door convertible made in 1966 in St. Louis and 121420 is the production sequence number, but I can't confirm or deny that was the origianl engine. Perhaps you could check the motor serial numbers if you could find them. That could be a tougher task. You might wanna check out... http://www.vettesite.com/vin.asp. That year apparently did come with the 427.