I towed with a 2008 V8 4Runner for a few years. I also owned a 2009 with the V6. They are very very solid vehicles and would be more reliable and more capable for towing than an Explorer, IMHO. I know a guy on a 4Runner forum I used to frequent who has 400K+ miles on a 4Runner and still going.
A V8 was an option from 2003 through 2009, same V8 that is in the Land Rover and the Lexus SUV. If you are thinking of used, buy one with the V8. The gas mileage isn't much different from the V6 and it's a much better towing machine, plus has a proper frame hitch from the factory. The V6 OEM hitch design was unimpressive and I wouldn't tow with it. I live in AZ so tranny heat when towing can be an issue. I removed the OEM trans cooler and put a larger aftermarket cooler on.
Good luck!
