TYpical SW rigs have in the 2200-2600 lbs EMPTY on the RA. You will have about 300-500 lbs available on the FA. The RA plus FA max loads will be around 15% MORE than the manufacture GVWR. Do not ask why, been debated sooooooo many times on here.
From a LEGAL stand point, you will most always get the max axel load, RVnet wt police will give you the gvwr to work with. If you have a paid for ton license, that is what an LEO/CVEO will give you if pulled over.
Reality is, a SW GM truck will have in the 3-4000 lbs range to work with for passengers, hitch wt etc. Majority will be on the RA.
These numbers are from my experience with GM's going back to my first NEW one in 81. RA empty numbers vary little between cab models, FA wts DO vary a bunch in the empty FA numbers. Example, my 2000 reg cab has all of 2900 on the fa, my 96 diesel CC model had 2400, both in the 2200-2300 lbs range on the rear.
Marty