My 2017 CCLB 350 Platinum had a payload capacity of 3,2xx lbs. Granted that's about as low as you can go in a 350, but the numbers Ford quotes will be for stripper XL work trucks

 

Check the Actual Regular Production Option Content Weight table attached to my message. The options don't add that much weight to subtract from available payload, and the worksheet attached adds the options to the payload calculation.