New G3 Hemi Block...

Speedmaster has had one for a while now.They even sell it through the major performance parts houses.
Chrysler 6.1L Hemi Gen 3 3.927 DH-9.239 Billet Main Iron Engine Block

Is that not a stock block?

My guess is that most Mopar guys will cry foul at the price of the Dart block. A 500" Gen III sounds interesting though.