Inner fenders.
The original 49 truck had inner fenders that bolted to the top edge of the outer fenders along the top edge, the radiator support at the front, and somewhere near the door on the back edge. I've owned 3 or 4 of this era Dodge trucks over the years, and have never seen a complete inner fender for either side! I've seen parts and pieces of their remains, but never a complete version. Originally, Dodge never painted them, and they just didn't survive very well, at least around here.
Since the goal was to drive this truck year around, not having inner fenders really wasn't an option. When I built my 50 all those years ago, I just took a big hunk of 18 gauge, bent it into a big curve, and added another piece of sheet metal to bolt it to the outer fender at the original location. It was OK, but there was more space available on that truck (it had 6" of fender clearance above the tire) then there is on this one. A new plan was required.
My donor Dakota actually had decent inner fenders, and they actually would match the current frame, but they were not quite wide enough because of the shape of the actual Dakota fender. To see if the Dakota inner fenders will even be a starting point, you need to hold them in place and evaluate.
Pic 1, Here we see the Dakota inner fender sitting on the tire. This pic is the driver side, most of the rest of the pics are of the passenger side. I don't have a pic of the inner fender laying on the tire on the passenger side, so you will have to believe me when I tell you it looked about the same. One thing I do want to point out on this pic is the angle the firewall makes at the floor level (just above the back edge of the tire). Hind sight is 2020. I should have removed about 2" off the sharp angle. That is where my slight tire rub is on that inner fender on both sides of the truck.
Pic 2, There is a lot going on here. 1st, that angle iron you see that is clamped to the front panel and to the firewall flange is what is holding the front panel in place. It is bolted at the bottom, but the outer fender locates the top. For this to work, I'm going to have to be sure the front panel is properly located. You can't see it in this pic, but the other side got braced also. A couple of other things, the coffee can on the Dakota inner fender is the carbon canister, it is bolted in its original location on the Dakota inner fender (and remained at that location). Notice the upward bend on the inner fender just outside of the carbon canister? That entire edge of the inner Dakota fender bent up in the same fashion, front to rear (you can also see the bent inner fender at the rear edge of the inner fender). The missing area between was rusted out on the Dakota part (both sides of the truck). Between the pretty bar stock clamped to the fender mount (and a lower bracket bolted up with a piece of scrap metal), the inner fender is held in place at the rear, and the ratchet strap hooked to the carbon canister bracket, going over the top of the angle iron holding the front panel in place and connected to something on the motor at the front has the inner fender in the proper location to the frame.
Pic 3, This is a better view of the clamped bar stock, and a lower bracket that is bolted through an existing hole on the inner fender, and the cab mount bracket that the outer fender would be bolted to. With a bit of imagination, its not hard to see why the tires rub on the inner fenders by looking at the position of the inner fender, the firewall/floor angle, and the tire position. I wish I would have noticed that then.
Pic 4, This gives you an idea how the frame and the inner fender align. The bolt you see about the center of the pic is the top of the shock. The rubber flap on the inner fender rests between the tire and the shock.