Towards the top end, yes, but within reason, if you drive reasonably. Mine is almost that weight, and it hauls just fine, so long as I load it properly, to keep 10-15% of the weight on the hitch. If I get any trailer sway, it is because I have loaded it improperly. I can usually adjust it with the amount of water in the tank, but I usually tow with all tanks empty. (except my fuel tank, LOL!)
There are several people on here who tow bigger trailers than ours, and claim no difficulties.
Caveats:
1. Highly recommend a weight-distributing hitch, with anti-sway feature. It is a very scary thing to have that heavy trailer controlling the car at highway speed!
2. You should definitely have brakes on the trailer, and a brake controller on your dashboard. Learn how to use it.
I am thinking air bags in the rear springs would also help with the 4Runner. You will get tired of on-coming drivers flashing their lights at you all the time! They will enable you to carry a heavier load in the bag, a higher tongue weight, and make the whole packege safer.
Some people on this forum have gone with an extra tranny cooler, but others say they have no over-heating issues pulling a big trailer in the mountains, with just the tranny cooler that comes with the truck. I will monitor my T4R (when I get it) with a Scangauge , before deciding if an extra tranny cooler is necessary.
Hope this helps (no experience with 4Runner, I am towing with an FJ, but quite a few years towing experience)