Want to make a cheap wood flatbed for my B2200, help please?

Hi, I've got a 1983 Diesel Mazda B2200. I am making a custom hardsided pop up camper to go on the back, but first I need to make a cheap flatbed. I don't know where to start really. I am thinking it will involve unbolting the bed, making some raisers for the bed mounts and laying 2x4's across it.

I searched already, didn't find much in the way of instruction. Anything I should know? Anything I need to watch out for or unhook? Anyone got a diagram? I have no repair manual yet [anyone got a download link or someone to message?]

Thanks =]

Mine is an 86-93, check out the project suki thread, I've got some in progress build pics of mine. It's a steel frame with 2x6 planks. Might give you an idea where to start.