If you want to know what your vehicle is really worth, look at completed sales on Ebay, and that is a solid baseline for what real world private party value is.
I did some conversions based on known dimensions, the 3 inch trailer hitch and the cooler width, I came back with the cargo width (at tailgate) of 47" based on the hitch conversion, 46" based on fridge. Although of course an estimate, I think these are likely to be accurate within a deviation of...