I'm new to the forum starting today. My situation is similar to VAredRAM's except that I have an '09 Ram 3500HD 4WD SRW pickup. I made an assumption that I'd be able to carry the AF990 w/o any issues...
We looked at the AF 990 when we had our '06 Dodge 3500 SRW. It (the truck)had a 2700 lb payload. The 990 is very heavy for an SRW. Doing all the calculations, we would have been over 1000 lbs above GVWR. You're in DRW territory.
Good luck with all the mods you're going to need. Though, some folks will say you'll be fine. Hope you don't have to stop too quickly...especially with horses in tow.