2016 Ford Superduty - Aluminium

1 lbs weight loss would equal 1 lbs payload gained with the same suspension. .. however it's not that simple. Ford will have to change the suspension calibration to be within their acceptable limits for ride quality. Losing that much weight would reduce ride quality significantly. That's very important to Ford as many many trucks never haul anything other than passengers. So while you may lose 700lbs, you won't gain 700lbs of payload.