You could, but it really leaves a massive hole. If you're driving in wet/rainy/snowy stuff it may cause a lot of spray. In addition it would also help stop rocks from coming up near the cab or hitting corner windows. My 2 cents, put something in there. AS I was welding on my running boards the other day, I wondered how a set of splash aprons might look if they were simply square? It would be a whole lot easier to build and may not look half bad. Or how about this? Come up 1 inch off the running board, bend 45', 2-3"run, bend 45, and finish up to the bed....Huh maybe I'll try this two if my originals don't survive the bead blaster!
1970 Chevrolet C10 Grandpa's -- My first truck -- In progress to shiny Follow the build in the Project Journal 1950 Chevrolet 1-Ton Dually "Ole Red Girl" In the Stovebolt Gallery More pictures here 1951 GMC 9430 1 ton dually--Shiny! | 1972 Chevrolet C20- Rusty- the puzzle box lid for the C10 | 1962 AMC Rambler American- my wife's Parts trucks- 1951 GMC 9300 | 1951-GMC 9430 | 1951- Chevrolet 1300