If you look closely, you can see a vertical rubber roll. That is actually left over bulb seal. I fabricated an aluminum panel that's riveted to the frame and extend inward holding the bulb seal and forming a nice seal to keep water and dirt out of the gap between the frame and the body. Before installing the panel I applied some expanding foam strip that came with the kit.

Note the blacked out inner fender and splash panels. I used truck bedliner for that.

Tip - The bedliner won't stick to the silicon used to seal the gaps in the chassis. To overcome this, I used 3M spray rubberized undercoating first on the silicon and then coated that with the bedliner. It sticks well now.