First off, this is not a fair comparison. A 6.1 Hemi is 370 cu-in. So it is at a 56 cu-in disadvantage. If both engines had the same displacement the newer engine would dominate the 426. It is made of lighter, stronger, lower friction parts. It is cooled more effectively, has better ignition, and then there is the rather important matter of fuel injection vs. carburetion.
This is like when sports fans compare teams from different eras. Take these two Super Bowl champions from each era the Hemi was available; the 1968 Jets and the 2008 Steelers. There isn't a single player on the 1968 Jets that would have even been invited to the 2008 Steeler training camp, much less make the team. The current players are so much bigger/faster/stronger it isn't even close. I doubt any 1968 Jet would even see the field for any 2008 D1 college team. Same with the Hemis. Superior advances made in the last 40 years.