I just grabbed a picture off the internet to show what it was. It's just a slanty manifold that has been cut. Hell people still do it today to V8 manifolds.
Yea the carb that can on that engine was not the greatest for sure. I have seen guys put the Weber type carb on those manifolds just to make the car more driver friendly. Cut it open like his picture, then the adapter, then the 4 barrel. Anything goes! LOL
Those two do not look the same at all. That sure looks like cast to me. Plus the numbers are not even close. But thanks for posting it. Marine stuff is different for sure.