How to increase load capacity

Heavy duty rear springs or overload shocks should help. Air springs are a option. Heavy duty shocks both front and back will help keep things under control.

Heavy duty tires would be the next step. If you can get load range E tires and pump them up to the max when you need to carry a heavy load. Even with heavy duty tires and springs you will be limited to about 2,000 pounds.

Thanks for the responses. Where can you get heavy duty rear (leaf?) springs?

Do an internet search ---- http://www.sdtrucksprings.com/leaf- springs/truck-suv/toyota/tacoma