air shocks can be used with an explorer as far as i know. as far as my trailer though. i was hauling about a ton that day... assuming that each hay bale was 40lb (we had 50 of them). so if you figure that with your 10% rule of thumb, that's at least 200lb on the tongue. also, there should be a load rating on the plastic trim around your bumper hitch. my 2000 Explorer Sport says "350lb maximum tongue weight, 3500lb gross trailer weight". and there should be more specific information on the inside of your driver side door (on the label below the latch). there should also be towing information for your specific model in your manual (pages 181-185). all you have to do is match your drive-train, and engine with these charts and it will tell you the GCWR (Gross Combined Weight Rating - the total weight of the vehicle, passengers, cargo, trailer, and trailer load), as well as the Trailer Weight Range my explorer is a...
4x2 automatic transmission (page 183)
4.0L SOHC Engine
3.73 rear axle gears
so....the manual says that....
my GCWR is 10,000 pounds and my Trailer Weight Range is from 0 to
5,940 pounds that means that the total load of my explorer and trailer together should not exceed 10,000 pounds and that i can tow a trailer that weighs up to 5,940 pounds (assuming the explorer, passengers, and cargo do not weigh more than 4,060 pounds, as this would exceed the GCWR of 10,000 pounds, when combined with a 5,940 pound trailer)
as far as tongue weight goes, the recommended tongue weight for the bumper, is printed right around your trailer ball, and as i said earlier, the maximum recommended is 350 pounds so you should be in no danger by towing 320 pounds.