Your non-negotiables are kinda limiting. 6K tow rating rules out the midsize SUV (Forerunner, Explorer type) I think. So you gotta go to the Tundra, F150, Silverado, Tahoe type size. But then you bump up against your fuel economy and maneuverability requirements. Modern trucks have kinda goofy bed/cab configurations in my opinion. Sounds like you would need what used to be called a extended cab, regular bed which can be hard to find.
What's the Sequoia's real world MPG and current miles? Can the tow rating come down to 4.5 to 5K?
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