[Warpath]

Do you have a metal cage frame for the box? That would add a decent amount of weight.

Air ride rear is going to be rated at 20,000 max, unless it was used in some sort of special application.

You really need to swing by a cat scale and get that thing weighted.

Also get the vin # and call ford truck dealer and they will be able to get you the spec's on the chassis. You definetly want to know what your front & rear axle ratings are. It is going to make is much easier to get the ride figured out with this information.

Things like tire pressure can be adjusted which can be huge in the ride department. Alot of tire shops will put 120 psi in your tires, when spec's show 95 psi is all that is required and I can tell you the ride will be night and day. But with out a weight ticket I wouldn't mess with anything. When you get weighted be sure to pull through twice and drop one side off the scale (if you can) to get a side to side weight.

With air-ride rear you really should be riding better than the front end, specially with weight on it.