Tire and wheel size

I own a Z71 4x4 with a six inch suspension lift. I currently have 35x12.5-20R BF Goodrich A/T tires and 20x9" wheels with a +12 offset. There is no rubbing. I am gearing up to replace the wheels on the truck and have been told by several tire/wheel dealers I can only run a +18 or +12 offset with that tire size on that truck, with that lift. One dealer advised me a 0 offset would not work, nor any negative offsets.
Can I run a 20x9" wheel with a 0 offset, or any negative offsets with a 35x12.5 tire on that truck without major trimming?