It'd be a big job. There never was a factory installed Hemi in the Dakota, the chassis wasn't designed for it. IIRC the right exhaust manifold would interfere with the upper control arm mount, and the left would interfere with the intermediate steering shaft. Also IIRC there are issues with placing the catalytic converters and routing the exhaust downstream from there.
Yep, I totally missed that this was a Dakota. People have stuffed Hemis into the 1997-2004 Dakotas with a good bit of work. I don't know how relevant that is to the 2005+ Dakota though other than it won't fit easily.