I've never heard of a V6 Explorer having more than 5000 lbs MAX tow rating. Maybe 5500 (?). But that's with absolutely nothing but a driver in the Explorer.
Either way, the first thing I would do is secure the use of a vehicle with at least 6500 lbs towing capacity.
If you believe that the 4.10 gearing gives you more capacity (I don't), you might convince yourself otherwise. But if that's the case, then please, please, please...be sure that this trailer has it's own braking system. If surge brakes, make sure they have been maintained, and test them (with the manual apply lever).
If they are electric brakes, then your Explorer will need a bunch of extra wiring installed, and an electric brake controller installed, in order to work those brakes.
If you try a 6000 lbs trailer with functioning brakes, you are taking a moderate to high risk.
If you try 6000 lbs without functioning trailer brakes, it's a death wish for you and anyone else on the highway.