I’d say another important aspect that I don’t see much reference to is drag. I have a large cargo trailer, it’s wider and taller than the 4Runner. Even when it’s light and empty it causes a lot more struggle for the 4Runner due to the large flat surfaces. When I tow with it I don’t usually go above 55-60 and stay in 4th gear. If it’s up an incline then maybe even slower than that. That being said, I don’t try the beat the crap out of my 4Runner so I’m not comfortable cruising in the high 3k+ rpms. I’ll just go slower, or use the diesel that is meant to tow.