When buying a used pickup bed, length, style and condition should be considered. If the truck bed is replacing an existing one on a truck, buying one that fits without too many alterations is helpful.
Trucks either have short or long beds. Short beds are usually between 5 and 6 feet long on compact and mid-size trucks. On standard pickups, they are usually 6.5 feet. Long beds are usually 7 to 8 feet long and are generally used in commercial settings or for hauling large cab-over RV campers. If the intent is to build a longer truck, the wheelbase should be checked to make sure the new bed is compatible.
Today's trucks offer two main styles of beds. One, sometimes called "styleside," has straight sides from the back of the cab to the tailgate. The other is the "stepside" that has steps on one or both sides of the rear wheels. The styleside is more aerodynamic, but the stepside is easier to climb into.
Checking the truck bed for rust, dents, holes and damage is a must. If a truck bed needs extensive body repair before it is usable, it may not be cost effective. Some vintage pickups have truck beds made of wood. These should be checked for wood rot and termites, depending on how long they've been in storage. Since vintage truck beds are hard to come by, it may be worth the expense of restoration.