When you look at a tow guide you can understand why the confusion, there are abou 60 entries for an 06 Dodge 2500. cab design, bed design, engine, diff ratio, 2wd 4wd etc.
The 373 cuts you back quite a bit. For instance, a 2500 QC LB 4WD with Hemi is 8650, while the same truck in manual trans and a 410 is 10650. Yhe guides we have to work with don't give much more as far as bed loading etc.
If you post the info I'll get you the info I have. Remember GCVWR, C being combined. Bigger number, but one not to exceed. We have a 1000 pound guideline for packed gear and water etc. Need at least that much capacity. However based on the trailer, it is just a guideline. A toy hauler would need much more, a little trailer, a little less. A 12' trailer probably doesn't have 1000 of Cargo Carrying Capacity.
Our sales guys are schooled in this stuff, and we will not be allowed to sell something outside of the parameters. Of course the argument can still be that the 1,000 is way too liberal. This is why I talk about this issue with my customer.