I know a dog trainer that drives gravel roads daily. He put one in the back of his Chevy truck with no topper or anything to stop dust. Been on for over 3 months and his drawers are clean.
I have a Decked drawer system on my 2019 Tundra.
Great organization via partitions or cases.
I am able to store 4 soft cased shotguns in the draw or more if I create a rack mount to hold the guns vertical without their cases.
Sorta unrelated but I picked up a well used decked crossover toolbox this fall for my tundra. Nice unit. Don’t think I would have a problem buying a new one.
I have the original Decked system in my truck and love it. I don't stock it with hunting items because it has my tools in it. I drive a lot of dirt roads and there is some dust from 4 1/2 years of use but not enough to worry about it. I bought their gun mounts but haven't used them. If I were to put guns in the drawers I would have them in a soft case and zip them closed.
The only "problem" I have is with my topper that is cab height I only have 22" from top of deck to topper door opening.