My father had a '79 F150 with a 8 foot bed. It also had a shell that was ~1' above the cab.
He built the bed in thirds. Left 1/3 and right 1/3 were permanent. The bed were lids that had a hinge, lifted up, you could store anything, so he had two beds, the center was left open, like an aisle. However, on the inside of the two sides he left a lip. This lip held a flat board(which was removeable obviously, thus making the entire area one large bed) for when he had children. He also built a shelf/cabinet in the top part. He also had 2 lighs and a fan.
Hope that helps some. Sorry, no pictures, the truck has been sold. Was an awesome truck though. I can maybe draw a picture if what I'm saying doesn't make since.
Oh Crap! Handle- Standard Equipment
"If you need a knife to open your knife, you've bought the wrong knife". -Tedder