Truck manufacturers typically sell several different versions of the same model with varying degrees of payload capacity. This capacity is noted in the model number, such as Chevrolet C/K 1500, 2500, and 3500. On some models, these numbers are the maximum rated load (1500, 2500, and 3500 pounds). Increasing the rated payload capacity is a matter of upgrading the suspension and drive-line hardware, and may take the average backyard mechanic several days to complete.
Upgrade the rear springs. This will have the most dramatic effect on load carrying capacity. Springs with a higher rate will have more leafs (in leaf spring designs), or a thicker coil, raising the amount of weight that can be loaded safely onto the bed.
Add coil-over shock absorbers. The stock shocks reduce bumps and swaying when the load is in motion. Replacing the shocks with coil-over models will allow heavier loads, up to 500 pounds per shock.
Replace the stock bed with a longer version for the same model. Most pickup trucks have long-bed options, and if the truck was ordered with a short bed, it can be easily replaced with a longer one. Most times this upgrade can be a simple bolt-on operation.
Add bed racks or rails. Most times the longer, awkward loads can be placed onto side-mounted bed racks to allow more room in the bed for other items.
Add a trailer. The payload capacity of the truck can be increased two-fold by the addition of a trailer. Some trailers are actually re-used truck beds themselves, and may even be larger than the bed on the truck. Tow rates are normally higher than bed payload rates, and up to several tons can be safely towed by some trucks.
