Unless I missed something,(possible) it says 283. An L79 would have been a 327 with the recessed oil filter boss for the chevy ll application. Not all 12 bolt Chevy ll rears were L79, and none that I remember were 4 series, although it may have been an option.
Most I think were 3.31, but I'm going off memory.
I think you'd need doc's to prove the L79 claim. But it's still a cool piece. I don't think you can build it for that price.