1969 Z28 ID Help

[Als 70 L78 Nova]

Thanks for all of the input. If indeed there is no vin stamp anywhere on the engine as th owner states but there is a stamp on the pad indicating it is a DZ engine and the X77 is on the cowl, how would this effect the value. i.e. Would this now be considered a real 69 Z28 with a correct DZ engine but not be considered a "matching numbers" car? FYI, there is no paperwork that goes with the car. Just trying to put a value on the car as it stands. Thanks