Stefan SSing, I just think that those motors are quite pricey to put together, and to try to run the old school Dampener, when your going to buzz it up, is a little tooooo Much of a gamble now days.
Check with a couple of the Hemi Builders and see what they say.
But my personal preference would be to use an SFI Dampener, and those work well threw out the RPM range.
But I do think it's cool that you want to run a somewhat period correct 426 Hemi... Thats Awesome.
Just if you done go that route keep a close eye on it.
Best of luck.