I put 400 pounds in my recently restored 3100's bed and was amazed at how much the springs deflected given their robust appearance. If i loaded it with 1000 pounds the deflection it might have would be extreme, with the rear of the truck really sagging. The load was wood heating pellets. With my GM SUV rated at 1/2 ton, with a thousand pounds it barely is noticeable! See the pictures. one with no load and the other with 400 pounds.
Best regards,
Joe
'49 3100 "Sweet Caroline" because the truck has fabulous curves .... like Caroline!