In hotrodders.com October 2007 was the same question, but no answers:
I'm looking to find a new aftermarket small block chrysler, preferably a 360. If at all possible, I would like to find an aluminum block. I've tried World, Dart, and Mopar Performance Parts and I'm unable to find one that is better than stock specs. Where can I find an aftermarket block that can run big horsepower?