Naylor99-
I just went and took some measurements.....
Overall length: 56"
Overall width: 48"
Useable length: 55.5"
Useable width: 45"
Shelf Height: 4" ( Loose this much from overall height)
Travel dist: 40.5" ( I did a mod to bring mine to 48.5")
The 40.5" travel distance is actually how much the bed actually slides out, I did a mod on mine to slide it out 48.5", though it may not seem a big difference, those 8" makes it much more comfortable to get to the very end of the shelf.
As for installation... it is attached with 2 brackets (one on each side) to the front lower tie downs, no drilling whatsoever is required, when you need to remove it, just slide out and remove the shelf first, then open the midgate and remove both brackets and slide out the frame. I have done it all by myself, though it is much easier with 2 persons.
Also, the deck is covered with some cheap commercial carpet, however, you may wish to install a rubber bed mat on it ( I did ) otherwise any and every thing you put back there will be sliding all over. By the time you are thru with it, figure you may have spent another $100 on top of whatever you paid for it.
Let me know if I can be of further help.
John