426 Hemi or 5.7 Hemi for a Duster

Cheapest and easiest? The new Hemi.
Coolest? 426 Hemi.
I wouldn't have said this 10 years ago, but as technology and the aftermarket moves forward, you can get a lot of the parts you need for this swap pretty easily and affordably.
There are a lot of written off vehicles to choose from to get complete engines etc. from now.
I would guess that to get the parts to install a 426 style Hemi properly would be at least double.
The engines alone aren't cheap!