It should be 10,000 lb gvwr for the D-Max if I remember correctly. The 6.0 gasser is 9,500 lb gvwr.
BUT..... It is possible he may have a little less available payload than I do because of the heavy D-Max. If you are considering the D-Max, even if you don't have a real heavy trailer now, seriously consider going with a 3500 SRW with the diesel. Will give you about 800lbs more payload, give or take the exact amount.
What is the payload amount listed in the drivers door jamb just for a comparison to our truck. Ours is a decently optioned LT, same cab/bed combo so it is somewhat close for option weight.
We have 2,75X lbs payload per the yellow sticker.