None of them... . Actually it doesn't matter, you can't lay 4x8 plywood flat in a Tacoma anyway. You have to use planks in the cutouts so you lay it across the wheel wells. I don't think any bed stiffeners would interfere with that. I'm not an expert, but don't you need those if you're putting a bunch of weight on the bed rails? Do you need them otherwise?Does anyone know if bed stiffeners are necessary for this generation? I'm assuming so, but does anyone know which ones will work with full sheets of plywood?