I have the same truck (2017) and just bought a toolbox. How did you mount yours with the channel rails running down each side? How did you fasten down your toolbox?
The model I bought fits between the rails with an inch or more clearance on each side. I used j bolts to secure the box but could not get a good bite to make it feel secure. I ended up adding a 1/4” lag bolt on each side to make sure it stays put.