Aluminum Engine in a Crate

[Jeep Guy]

New here. Short version. I bought a 68 Camaro, it came with a bunch of parts, one item is an engine block in a crate, that I am told was bought over the parts counter (parts guy name Smitty) in the 70's at Yenko Chevrolet, and it is an ZL1 . I have opened the crate, and found the Winters Foundry logo on the block and a magnet does not stick. At that time I still had a half of a UHaul truck full of parts to unload and my help was leaving, so I boxed the engine back up without even looking for a casting number. My plan is to reopen the crate this weekend and further inspect this engine. With that said; What am I looking for to identify this engine? Newspaper in crate dated 12/21/76 Shipping label is from Yenko Chevrolet. Sorry for picture quality, when uploading kept telling me file was too big, so i guess when I cropped it quality changed.