You can really use anything you want, as was mentioned you will have to finish it with something. I'm using Philippine Mahogany. I figure that if Chris-Craft can build their classic wood boats out of it I can use it for my bed. Besides it goes with the color of the truck.
You will want to use a hard wood, if it's too soft no matter what you put on it it's going to scratch.
Here's a list of a few I think would work well
Philippine Mahogany
Southern Yellow pine
Oak
Teak
Hounduran Mohogany
Maple
Ipe (pronounced e-pay) used in outdoor decking
Check your hardwood lumber store. Use what looks good to you. If you have the bucks the list is almost endless.
Good Luck
George
