Welcome boozer45, you probably would do all right on flat ground but your are really pushing it when it comes to hills. I have a 25FB and loaded to the max is 5500 Lbs that I use to pull with a 5.3ltr Yukon and it did fine. I moved up to a 6.0ltr 2500HD and it pulls that trailer like an empty aluminum can.
Any way looks like you just bought the truck so you might look at the 25RS-S. Another thing, I never pull with my holding tanks full and we only take what we need on trips, keeps the weight down from that gross figure.

