If you're asking whether the 4Runner
will tow it, the answer is yes. But if you're asking if the 4Runner
should tow it, the answer is no. You'd be well past the margin for safety.
I have a Tacoma with the same tow rating. My 17'
Bigfoot is too much trailer for it. It's within the tow ratings, and safe, but is maxed out. The tongue
weight of a 21 would put you way over your payload limit. I also notice that with any headwind, I might as well be towing a parachute. My Tacoma is a 3.4L V6.
I haven't measured my tongue
weight but looking at what similar trailers weigh, I figure 300-350 pounds. There is only one Bigfoot 21 listed in the "trailer weights in the real world" thread, a sticky at the top of the General Chat part of the forum. It's listed tongue weight:
1160 pounds! My guess is that's your entire payload limit. So you could tow this trailer...if your 4Runner can drive without you, without gas, and without a single item of gear.
I think that particular weight is an outlier, though.