treegump
Romans 3:22-24
they do offer a box built just for flatbeds that mounts on top of the bed and has a big pullout, it is built to last, but it costs about 800 bucks, obviously it doesn't take near that to built considering you can get complete flatbeds for 1000.
But no, i haven't seen a big pullout drawer idea like that, it sounds awesome though.
http://www.truck-tool-box.com/hd-series.php - is kind of what i'm talking about - but you've already got the bed. I want to build a bed that is 1 solid surface on top and put (4) 2' wide, 2' long toolboxes along the driver's and passenger side of the bed - and place the actual bed on top. Yes, the surface will be raised the depth of the box, but the tools will be secure, protected, and maximize your bed space. The only problem is - how to make the bed structurally sound. I'll try and draw up a sketch when I get a chance.