NWnative - you are correct, it THEORETICALLY has 4-500 lbs less payload than the gasser. On our second test ride we literally took it to the Pilot truck stop nearby and weighed it, then filled it with fuel to get the fuel weight.
Subtracting actual weight with fuel from the GVWR actually yields a payload number slightly above what is on the tire door sticker. IN any event I took all those numbers home to run my calculations, "cool off", and try to make the decision rationally. The GVWR numbers turned out to be a good fit for us (finally).