New to Mopar here..

Its a mystery, perhaps someone innocently lost the title or like has happned many times it went from hand to hand without being registered. My guess is, Someone got it who had a clear title to a 67 parts car so yanked the 68 info and put the 67 #s on the door. No good reason to pull the dash tag off a perfectly complete car like that. Not that I can think of.
We need a good close up of the vin tag on the door. can you tell if the door is different color underneath the current paint?
also if you don't feel like peeling up the trunk lip seal, you can lay in thetrunk and look up at it from the bottom. sometimes its stamped deep enough you can make it out in mirror. On a Road Runner and Duster its on the drivers side about 5 to 8 inches forward from the corner. At least the 194426 should be there somewhere.