I have a Betterbuilt diamond plated box in mine. They don't have the same dimensions as mine, but I have had mine for over 20 years. Mine fits perfectly between the wheel wells, and the front of the box. So well, I don't need to bolt it down. It was a miss order when I worked at the tire shop, and I got it at cost. But I had a 85 Nissan LB, so I had to strap it in to the tie downs. Because I didn't want to bolt it in place. Here is a link to what I have.
https://www.lifebetterbuilt.com/products/truck-boxes/ChestTruckBoxes/62012330
