That would rack work fine and super easy to install if there is no need to access guns rapidly. My main concern would be that there is no provision for keeping the gunstocks from getting together if you use the truck off road, but you could rig some sort of padded rest for the butts to take care of that.
I needed quicker access to the rifles yet wanted something easily removable for my pickup and couldn't find anything on the market to do that job. Ended up fabricating a
gun rack for utv that rests on the dash board, rear floorboard and rear seat, held in place between the bucket seats with 2 bungee cords. It was capable of carrying a bolt gun for driver & passenger and an AR in the middle & provided easy access for driver and passenger. Used carpet to pad all contact points between the rack/vehicle and the firearms. Nothing for looks, but worked as intended for 22 years, holding the firearms on & off road and the truck was no worse for the wear when it was removed.
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