Trailer or tow dolly?

And there's a difference between doing something once or twice in a bind and using it as your racecar tow vehicle on a regular basis. 3rd Gen 4Runners have shitty auto transmissions and rear axles to begin with. Subjecting them to big loads is asking for failure. Plus the rear suspension is too mushy for a big trailer load. The truck starts to feel real squirrely on the highway. The brakes totally suck too (with a trailer and a car behind you.)

At the very least you need to run an external trans cooler and get rid of the one that's in the radiator. The one that's in the radiator has a nasty habit of mixing coolant in with the auto trans fluid, which quickly kills the trans.