Pickup trucks can be ordered from the factory as “cab and chassis” units, which arrive with no bed whatsoever. This is done so the owner can take the truck to an outfitter and have a custom bed installed, such as a tool bed or flatbed, depending on the job role the truck fills. In the event you have a truck that already has a standard pickup bed on it, you can replace it with a flatbed in about an hour with a little elbow grease and some aid from a helper.
Remove the fasteners holding the fuel filler neck into the well in the side of the bed.
Climb into the bed and remove the four to eight bed bolts and washers holding the bed to the truck frame with the socket set. Depending on your make, model and year of truck, there may be more or less bolts, so remove them all.
Climb underneath and remove any U-bolts that may be attaching the truck bed to the frame. While underneath, disconnect the wiring harness leading to the tail lights and make sure it is out of the way for the bed removal and replacement.
Move to the left side of the truck, and have your helper stand in the corresponding spot on the right side. Depending on the size and weight of the bed, you may want to have up to three helpers.
Lift the truck bed off the frame, with you and your helper(s) lifting at the same time. Walk the bed backward off the truck and set it down in the space you have designated that is clear of the truck and will not interfere with moving the flatbed onto the frame.
With your helper’s aid, lift the flatbed and walk it over the frame. Make sure to line up the holes in the flatbed with the holes in the frame.
Install the bolts and washers through the flatbed and into the truck frame. When done, climb under and reinstall any U-bolts you may have removed in Step 2. Reconnect the wiring harness for the tail lights and attach the fuel filler neck.