Unfortunately, when you find a Ford Blitz in Australia, it often seems the engine has been pinched by a hotrodder sometime back in the 70's. When you do find an engine, chances are it's all rusted up or has a cracked block. Then, and only then when you have found a good block, you start the frustrating process of finding an engine builder who speaks fluent sidevalve. Good luck!
Mike's Sidevalve Supply in Adelaide will supply a fully rebuilt exchange flathead V8 for around $2750, plus freight, or they can rebuild yours if you wish to retain a particular engine number. This is for a basic, stock engine. If you want any performance work done, the price only goes up from there.