I'm considering doing something like that as well but haven't spent too much time trying to figure tings out ---- yet. But, with that said, take a look here for some ideas:
http://www.morryde.com/product-category/2-sliding-trays
Not cheap but after looking at the prices of slides that would be heavy duty enough, may be the way for me to go. Also, and without knowing the size of your cargo space (ours is huge) be aware that you may need access to whatever is behind any bulkheads you may need to access before anything permanent is put in the way, i.e. water pumps, wiring, furnaces, etc,etc, etc