I owned two separate small sized Nissan trucks and they were great for hauling. When I needed to haul full 4'x8' sheets of stuff I used a little box frame I made from 2"x6" lumber that I put near the tailgate so that sheets rested on that and the wheel wells.

I don't own a truck anymore and now my "hack" is to remove the middle seats from my minivan and fold down the back row seats. That creates enough room that I can fit full 4'x8' sheets in it (with zero room to spare). I've hauled drywall and plywood in it with no problem. I sometimes get weird looks from folks when I roll up to the back of my minivan with a cart of plywood at the big box store.