Numerous articles about the '05+ Dakota have made contradictory claims about the relationship of the Dakota's frame to the Durango, ranging from them being completely different designs to being the same design. I've wanted to know what the actual situation is, and tonight I finally found a Dakota and Durango parked side-by-side at a local Dodge dealer and was able to compare them (I would have used my own truck but I was driving the junker Ford when the opportunity presented itself.) The vehicles compared were an '06 TRX4 package 4x4 Dakota, and an '06 Durango 4x4, both with the 4.7L engine. I also looked at a Durango 4x4 with the Hemi. I focused on the front suspension area.

First I compared the spring type used:
Dakota: coil springs over shock absorbers
Durango: torsion bars

This in itself is enough to indicate that the frames are different weldments. The Dakota has upper spring perches that the Durango does not need, and these are not present on the Durango; the Durango has torsion bar mounts farther back on the frame that the Dakota does not need.

I also examined the crossmember between the lower control arm pivots:
Dakota: relatively larger, box shaped
Durango: relatively smaller, C-channel

Again, the difference was sufficient to indicate that the frames are different structures.

Then the depth of the frame rails, in the foot or so between the front suspension arms and the rear part of the front wheelwell:
Dakota: relatively taller (7-7.5"?)
Durango: relatively shorter (6"?)

My speculation is that the Dakota needs the taller frame shape due to the different loadings imposed on it from the coil springs vs. the torsion bars on the Durango.

I also looked at how much clearance there is between the exhaust manifold heat shield, and the bracket on the frame for the upper control arm pivot:
Dakota 4.7L: about 2 fingers width
Durango 4.7L: about 4 fingers width
Durango Hemi: about 2 fingers width

I assume from this that there would be very little, if any, clearance between the Hemi's exhaust manifold and the Dakota's upper control arm's mounting bracket.

I conclude that the Dakota's frame, while sharing many technologies of the Durango's, is not interchangeable with the Durango's, and that the width between the rails is quite likely narrower. I also conclude that installing the Hemi engine into the Dakota in a production environment could be challenging without revisions to either the engine, the frame, or both.

Next time, I'm bringing the tape measure.