Long time E150 owner
Randbo wrote:
Our van has a 5.4L V8 engine with a 3:55 gear ratio. It is rated at 12,000 pounds GCWR and has towing capacity of 7,000 pounds.
With that ratio, I am guessing you do NOT have the HD trailer tow option. The HD trailer tow option include a 3.73 rear axle, a HD radiator, and auxiliary transmission cooler and a 7 pin trailer connector in the rear plus break out wiring for the brake controller under the dash.
These are all NECESSARY if you are going to be towing over 4,000 lbs.
I am not a fan of air shocks, but you can add a leaf to the rear spring pack for very little cost.