An 87-96 Dakota frame is 38" wide on the outside (I just measured). That 38" width starts just behind the front tires and continues to the rear of the frame. It does kick up behind the back of the cab, in front of the rear axle and remains at the height above the rear axle to the end of the frame. There is a raised cross member where the fuel tank sits, located in front of the rear frame kick up that is the same height as the rear frame kick up.

An 87-90 Dakota comes with 5 bolt 4 1/2" wheel pattern. A 91-96 have a 6 bolt 4 1/2' wheel pattern, that can be changed by replacing the parts with the older stuff. The newer Dakotas use different frames. Gene