Here you go TINY-TRUCKER there are two screw drives one on the truck to make the bed go up and down. It raises the hinged block at the back which is also the block that the bed slides on. This set up is similar to the screw drives used in my dump trucks just not as much movement needed. The second screw drive is in the bed it's self and since the block is mounted to the truck the screw drive is moving the bed instead of the block like in a dump truck screw drive. The wires for the screw drive are fastened solid to the front of the bed and are pulled back to the center of the bed by a spring holding them tight when the bed is in the down position. as the bed rises the spring keeps tension on the wires and then the bed will travel back release the tension and the bed can then pull the wires back. With this set up there is plenty of wire for full travel of the bed. Here are the pics.
I hope this helps it is the best I can do and you were in luck that I mocked up the bed with a piece of clear lexan.
Thanks for looking.
Travis