[flatheadmurre]

Aluminum has its issues to but it aint close to cast iron in being sensitive to built in tension and cracking from that.
Cast iron with an odd shape (not uniform in thickness and shape) will cool unevenly and even if you put nickel and other alloys in, it will be a challenge.
To take on a project like casting a flathead block is a deep black hole that will eat you time and money for a long long time....i can just admire the people willing to do something like this.
Problem with making a better flathead block is that it will never be allowed in classic racing, so there´s another set of tooling to go authentic and improved.