Hi Tim,
It would hlep if you had the broken pieces or most of them. I has reminded me of a training course I was on once, when with MoD. It was run by Belzona, which is a manufacturer of chemical repair solutions and used extensively in industry. Do not compare this with metal putty or plastic metal. The chap showed photos of some examples of repair and related how an owner of a vintage tractor, contacted the company to see if their product would work on a frost damaged engine ( from the photos, it looked to be a Fordson Standard block). He was told to clean it up and an engineer would come out.......when he arrived, the guy had cleaned it up..by breaking out all the cracked parts and cleaning them, leaving a gaping hole similar to your photo. The job was a lot more complex now, but it was all pieced together using Belzona and never leaked.
So in answer to your question, it could be possible........at least it is not a pressurized cooling system so that helps.
Richard