How to identify a BlackBird Engine?

[Onbusy]

Hello,
I bought a Camaro SS from my father, who swapped in a Blackbird engine. He doesn't have any of the documentation from the donor car, but bought it from a guy he knew so he believed him that it was a real Blackbird engine. My Dad believed him, and I believe my Dad, but now I am trying to sell my Camaro SS and most of the potential buyers want proof of what the engine is. Is there any way to prove/identify the engine as a Blackbird engine? What was swapped was the complete engine(Oil pan to intake), everything else is aftermarket (SLP Long Tube Headers, SLP air box, Vigilante 3200 stall lockup Torque Converter, Monster 4L60E, custom tune). Pretty sure it is the 380 version, not any of the upgrades.

Thanks,
Ryan