Also depends on what kind of roads and hills you'll have to pull the trailer up. I pull a 2200lb pop-up from time to time in the summer with my truck, and it pulls amazingly well on flat land. I'm sure if that trailer was closer to 3500-4000lbs the 4Runner would still be good at towing, obviously your acceleration would be down to nothing.
However, going up steep, long roads (like driving up into the mountains here in Colorado) is tasking for the truck. It can do it, don't get me wrong, but there will be times I'll slow down to 40mph and in second or third gear to keep moving.
If long steep hills aren't a concern for where you'll be pulling a trailer then the 4Runner can easily pull a weight up to around 4000lb (and probably up to 5000lbs too, but I personally don't like pulling anything that heavy with a V6). If they are or you're worried about the need for speed then you may want to look at a V8. I myself am contemplating a V8 truck myself just because of the mountain driving I need to do to get to some of my favorite off-road camping spots.
...I wonder if a Chevy 350 will fit in our trucks...