There has been a fair amount of talk on aluminum FE block quality lately. Brent has quit building them because of all the quality issues. It takes a lot more skill and a much better shop to cast aluminum than iron. It is my understanding that humidity is one of the big issues with porosity. I know one fellow only cast aluminum in the winter time, when humidity was low. I wouldn't doubt they are trying to cast aluminum in a rain forest where labor is cheap.
I happened to run into this youtube video of Kirkham machining a solid billet of aluminum. At least in theory, this should eliminate all these issues.
https://www.youtube.com/watch?v=8KLNJ8d8Vqc
I remember Dave had a thread going on this, but he left the company. So what ever happened to this project?