The answer to this question is VERY simple.........PROFIT MARGIN. Dart, World, Brodix and any other number of companies could EASILY tool up and make both big and small Mopar blocks. Problem is, they can't sell enough of them. You guys seem to think the demand is high and that's wrong. The demand is not high even on this little website, much less the hobby in general. IF there was money to be made.......SOMEBODY would be making it.
Like it or hate it, Mopar people are notoriously known for NOT supporting the aftermarket and the available parts show that.........Sure, there is a boat load of mildy warmed over factory style heads out there, but there ain't a nickels worth of difference in any of them. So why is THAT area so well supported and nothing else?.........because THAT is what the majority of Mopar people buy and do. Mildy warmed over stock type stuff. There hasn't been a serious effort Big block head is decades and won't be, because there is nobody to buy them