1970 z/28 purchased at yenko chevrolet

[Stefano]

Based on the "N" in the vin and not an "L", it should be a Norwood Built Camaro. I would say that it is not a Z28. I have never seen a documented '70 Z28 without the designation on the trim tag, but CRG will have much more difinative info for you. Your protecto plate should identify Z28 or not, as well.
Yenko sold Regular cars and Muscle cars to SuperCars at a ratio of approx, 75-100 /to one (just an estimation).

FYI, Sometimes the Z28 designation is very faint and I have had to carefully remove all the paint to see it properly.