Just throwing this out there, I hauled things way heavier then that in the bed of my truck that never should of been put in it. I used my truck like it was a super duty at times. I pulled a Ford 5000 tractor on a trailer with my truck and got on the park way and got my truck up to 70, and it did great. As far as the bed goes I had it full of dirt once, and several times I had a combine fill my truck up full of corn, and corn isn't light by no means.

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2004 Ford F150 Automatic FX4 SuperCrew 5.4L 3V Triton V8, No Muffler, true dual straight pipes, 3.73 Gears, 18" rims with Wrangler A/T's
White 2004 Ford Ranger XL, Auto, 4.0 SOHC, 4x4 Base Model, 16" Explorer Rims. 3.73 Gears, No muffler(Sold)
White 1997 Ford Expedition XLT 3inch Suspension lift, 38 Firestone M/T's 98 4.6L Police Interceptor high flow injectors, Super 44, brand new rebuilt transmission, with 3.73 gears(Not mine no more)