Curtis,
When I was looking for a flat bed a few months ago I did a search using "truck beds" and found many manufacturers. I remember finding one that built aluminum beds but can't remember the manufacturer's name.
I learned a lesson about flat beds that I will pass on to save you some possible grief. They are not quite as handy as they appear to someone, like I was, accustomed to pulling with a pickup bed.
The reason is a due to construction a flatbed sits about 6" or 8" taller than a pickup bed floor so pickup truck towing equipment like hitches, tool boxes, and fuel tanks are too tall for proper towing height or adequate clearance when installed on a flat bed. I had to have my 20K Reese hitch cut down and shortened by 4" to allow towing my 5W on a flatbed.
The reason for this is flatbeds are built with 4" channel frame rails running fore and aft that sit on top of the truck's frame rails. Then a flat bed uses 3" channel side to side frame rails sitting on top of the 4" channel rails. When you add the spacers the installer usually installs on top of the truck's frame rails and the thickness of the bed deck you raise the height of the bed deck 7" to 8" from the top of the frame rails. It will be worse with a pickup frame because your frame rails are not straight like the rails on a cab and chassis so spacers or brackets will be required which will raise the bed even more.
Here are the numbers: My 3500 cab and chassis was delivered with the top of the frame rails at about 33" from the pavement. Add 7. 5" for the C&M bed and the bed deck is 40. 5". A typical 5W king pin plate is at about 48". Factor in a 2" squat on a cab and chassis when loaded, more like 4" squat with a pickup, and you have only 8" to 10" of vertical height for the hitch.