If I remember, the Dakota drops at the firewall and kicks back up behind the cab where the box would sit. If you trim off the "ears" for the Dakota front box mounts, and remove the gas tank cross member, you will only be left with the high part above the rear axle. If you don't need the amount of rear suspension travel the Dakota has it shouldn't be a huge deal to modify the rear of the Dakota frame. Even if you "filled" the dip on the Dakota frame to make it flat, you should lower the panel by several inches, right? The panel's rear floor is wood anyway, guess it depends on what you want your rear floor to look like and what your planning on doing with the back of the panel.

Somewhere between these two extremes there should be a happy comprimise. With anything I've ever seen, the lower you want to go, the more modifications need to take place. How low do you want to go? Pictures would help a bunch. My old mind gets a bit foggy. Gene