I don't know what scale you used, but I think it might be skewed...
The one I used was at the dump when I went there (on the way out)
My truck, on 33's with steel wheels, and me and my dad in it (180lbs each), and about half a tank of gas, weighed in RIGHT around 4000. I think it might have been 3985 or soemthing if I recall.
And, as you can see in my sig, I'm pretty sure our rigs are very similar option-wise, except for the fact that you have a SAS in the front, correct?
here is a source:
http://autos.aol.com/cars-Ford-Ranger-2008/available-trims
Sport 4dr 4x4 Super Cab Styleside 6 ft. box 125.7 in. WB
Horsepower: 207 @ 5,250 rpm
Torque: 238 @ 3,000 rpm
Transmission: 5-spd man w/OD
Curb Weight: 3,606 lbs.
Fuel Type: regular unleaded'
Granted it is a new truck, but that pretty much confirms my numbers. Add 360lbs for people, and half a tank of gas, and you get right around 4000lbs.
And to keep it on topic, that is an awsome truck. It cool to see a bed that is not the standard beds, yet not a flatbed! And it is daimond plate, which makes it even cooler haha. Do you really daily Drive it??? If so, that is some dedication. I am not sure I'd drive that on the street, but that's just me.