Join Date: Oct 2009
Location: Just south of sanity
I wouldn't recommend pulling anything larger than a utility trailer with a 4Runner, even if it's a 6 cylinder.
It's not the pulling I'd be worried about, but the stopping. 4Runners just aren't heavy enough to stop a loaded horse trailer, especially if you need to stop in a hurry.
You can use a 6 cylinder vehicle to tow with, but you'd need a very small or very light trailer, and only haul 1 horse at a time. Either an extremely small steel/aluminum 2 horse bumper pull, or a Brenderup. Brenderups are fiberglass, so they're very light. They're also very expensive and pretty much impossible to find used.
If you can find that small/light trailer, make sure not only to have a towing package with a transmission cooler built into the truck, but a brake box and wiring harness so that you're utilizing the trailer's brakes along with the truck's when stopping.