I have a f150 and same issue with dust, I've since learned thar when I hit a gravel road, I flip the tonneau open. It creates a vacuum and covers everything in dust. I've seen a few company's make a rubber tailgate seal for about 20 bucks. Before I saw that I tried some tape in foam from home depot, it worked a while but now the foam is soaked and expanding, making my tailgate a little difficult to open. I found a used canipy nearby but it's just a cab height and I think I want a mid rise for a little extra room crawling in the back