I think I blew a hole in my timing cover 351w, help needed

I was driving my 1973 Mexican Mach 1 yesterday and lost all the coolant. it took me a few mins to find the problem. there is a hole that has blown out and I'm not sure exactly what part it is. its about 6" directly below where the main coolant hose connects to the manifold. it seems like it might be part of the timing cover, but I'm not sure. any help it telling me exactly what part this is with the hole in it would be appreciated. thanks

this car is a Mexican Mach 1 and spent most of its life by the ocean. the previous owner of 30 years had it sitting for a long time. the ethanol residue in the carb tells me that....so I'm sure your are right about the coolant corrosion. I have lots of surface corrosion, but thanks for the pointer on the internal corrosion issue and sourcing parts. appreciated