makes sense. Maybe the 2 new boxes could be positioned front and rear, instead of side to side? That way the "rear" box could have a lid opening to the back of the truck, and the "front" box could have the lid open just the opposite, toward the front seats??? Wouldn't that make it easier to access your stuff? Put the bigger/heavier stuff in the rear box so you don't have to try to drag it/squeeze it out from behind the seat?
Maybe even make the 2 side by side boxes have 4 lids, instead of just 2. 2 would open to the back, 2 to the front. that way you could access stuff from behind EITHER seat.