Payload "capacity/rating" - not even the OEM's agree?

So whats the "real" payload cap, 1300 or 1600?

Some manufacturers calculate the payload with the driver seat occupied. That might be part of the difference in numbers. Weighing the empty truck would then give a different number than what the manufacturer calculated with a driver and perhaps a tank of fuel. I don't see your frustration as payload is gross weight minus empty truck. Pretty simple really! Your entire post is a non issue. Maybe winter is getting to us.