The Dodge web site is pretty obscure, isn't it? I checked the numbers for the 2007 models at
http://www-5.dodge.com/vehsuite/TowingGuide.jsp# and found:
2007 Dakota SLT, Quad Cab, 4x2, 4.7-Liter High-Output V8 MPI Engine, Multi-Speed Overdrive Automatic Transmission
With 3.92 Axle Ratio You Can Tow 6950 lbs
Gross Vehicle Weight Rating(GVWR)=6010
Payload=1430
Curb Weight=4580
Curb WeightFront/Rear=2591/1989
GAWR Front/Rear=3100/3600
Gross Combination Weight Rating(GCWR)=11700
Does this have any relevance to your 2000 model? I don't know, but it might. I also found
http://www.allpar.com/reviews/dakota.html, a non-Dodge web site that says for the 2000 Dakota
Engine Transmission Towing Power
3.9 V6 NV-3500 five-speed, 42RE automatic 4,900 lb 175 hp, 225 lb-ft
4.7 V8 NV-3500 five-speed, 45RFE automatic 6,100 lb 235 hp, 295 lb-ft
5.9 V8 46RE automatic 6,350 lb 245 hp, 335 lb-ft.
This is more-or-less in line with your thinking and with the TM web site. It sounds like the discrepancy you describe is a really confusion between the 3.9L vs 4.7L engine.
In general, I would trust the manufacturer's web site over anyone else's.
Bill