You guys are dreaming if you think Dart is going to make a SB Mopar block. Maskin said as much during the Q&A at EM.
If you want a SB race block, it's Mopar or Ritter, period.
Now the company that has a vested interest in making a block, owns a foundry and is capable, would be Edelbrock...but when Chevy 409 heads take precedence over the Mopar Victor heads and pushed them back years, good luck with that.