The results are easily explained. 440 has too small ports stock.426 has too large ports stock....Increase the hemi by 100 CI and the results will be much better torque wise per CI.
The Chrysler engineers could've easily put a 4.250 stroke in the Hemi engine from the factory. There is enough room for it and they had the technology available to them. I don't know if they just didn't think of it or maybe they thought better of it. That would've been a 482 at the stock bore size and it probably would've been a monster on the street back in the 70's.
