After seeing the superbird, seems it would be easier that way than trying to mount the newer suspension on an old frame, newer motor with all related wiring, plus I would get a lot of the goodies that the charger has to offer. Like I said, I haven't decided yet, just weighing the options. The only thing is, I have 108" wheelbase while the charger has 120", width is relatively the same.
It is far cheaper to buy a rolling driving hemi powered car. Even a lightly salvaged one is ok. People that purchase crate hemis/trans are spending a whole lot of money extra that they don't need to. The same goes for engine/trans purchase alone. People know these hemis are getting popular for muscle car swaps so all of the hemis I've seen are 4-6 k. It makes more sense to me to purchase a complete car with everything you need for around that price range, that way you don't have to piece anything together, and you can take a trip to the dealer for almost everything you need. What I like with the complete cars is you can use everything, wiring, fuel tank, mounts etc.
I've looked at all of the newer car wheel bases, the new challenger is closest at 116 inch wheel base, the rest are 118-120 iirc. The guys that do this swap on old chargers have an easier time, as their existing wheel base is bigger, so they only need to find 5 inches to cut instead of an ebodies 10 inch to match wheel base.
With the floor pan layout on the new car you can cut it apart, remove 5" from the front pan and 5" from the rear pan. Lay the front over the rear and spot weld it. I've not seen that much, taken, but I don't see why it couldn't be done.