A metric $hit ton load of fab work and/or a wheel barrow full of money.
You would need to create new sub-frame cradles to hold the Viper suspension without compromising their geometry and then graft those into the Challenger uni-body structure and that doesn't even begin to address things like track width, frame width, ride height, wheel offset, and wheel well clearance along with all the associated sheet metal changes.
It might be a neat set up for simple wow factor, but not practical for anything but unlimited, open class competition.
