that upholstery job to cover the white of the truck looks very good.
you can use the 3 bolts sticking up to secure the rack on to the floor.
you can make a nice enclosure type rack where the amp can be mounted with a plexy glass front panel to view the amp with fans hidden on the side to keep it cool. you can run the fans of off relays hocked to a main power source and kicked on by the remote wire, so the fans kick on at the same time the amp gets power and off when the amp is off, you can also mount all your accessories like power distributor, power cap, if you have one, things of that sort in the rack as well, to keep everything clean looking, organized and safe.