With that bracket welded to the cab, and the inner fender bolted to it, I welded a piece of sheet metal to the front that went forward and bolted to the headlight cover piece. Then I added another brace at the bottom edge of the fender.
Pic 1, The bracket in this picture that is at the fender support was removed after the lower rear bracket was added. I don't have a good picture of that lower bracket, but it bolts to another bracket that got bolted to the cab mount bracket. With the addition of the rear bracket, the inner fender was pretty secure. There are 3 screws across the front, the bracket at the firewall, and the bracket across the back of the inner fender.
Pic 2, This is the fender, laying on my steel saw horses. The black part is the Dakota inner fender with the rubber flap at the top. The big rusty piece on the left side is the new piece I added to the front of the inner fender. It is plug welded to the inner fender in tis pic. Later it was fully welded. The rusty piece between the Dakota inner fender and the steel saw horse is the under side of the outer fender. I made pieces that filled the gap between the inner fender and the outer fender. At this point, everything is probably just clamped together. I see that the fender arch is not welded to the fender, I suspect this was the point I determined the fender would need the arch fully welded in place. After the arch was welded in, i could determine about what the filler piece would look like, but the fender and the inner fender would both need to be bolted in place. I added a strip to the outer edge of the inner fender, then welded tabs onto the outer fender to hold U-nuts. With the fenders and inner fenders bolted in place, I could drill the bolt holes through the inner fender and the tabs. The u-nut went on the tab, and the bolt passed through the inner fender and into the U-nut. There are 5 bolts holding the inner fender to the outer fender. When I first put it together, I had a little over lap between the inner and outer fenders when bolted together. I soon discovered that gave me a huge number of squeaks so both have been trimmed to eliminate the over lap except where the tabs are.
Pic 3, This is what the front junction between the headlight panel and the inner fender looks like from under the fender.
Pic 4, This is one of the bolts that hold the edge of the inner fender to the tab on the outer fender, from under the truck. The bottom of the pic it the inner fender, the top of the pic is the outer fender.