I thought I would share my experience to help some folks.
I own four econoline vans. 2 half tons, 2 E350 15 passenger vans.
On the half tons I had purchased the moog, and rancho steering stabilizers that bolt to the suspension arm for the passenger front wheel. I never was very happy with this, the suspension moving up and down affects this type of set up. I found out that the dual rear wheel ambulance models of the E350 have a steering stabilizer that bolts to the chassis instead of the suspension arm. I got one off a salvaged ambulance and tried it on my half ton van. Oreilly has the stabilizer for the origional Ford brackets at 34 bucks from monroe. It fits 1992 and up, with origional brackets.
The holes for the chassis bracket are already in the chassis, you have to use the chassis oblong hole to get to the bolt heads through the chassis to tighten that bracket. The other end bolts with a ford bracket on to the drag link.
The difference in the steering was immediately very good. Tracks better and less moving around. So I decided to put it on my 2002 E350 V10 and it steers like a mini van now. Stable, tracks better, less influenced by wind, and less correction. I just put one on my 2005 v10 and same great results.
My wife likes driving these vans now, hated driving them before, and that is saying something.
You can get the brackets from Ford if you ask for a 1999 E350 dual rear wheel ambulance package steering stabilizer brackets. I did not buy the ford stabilizer tube. The bracket for the chassis is $80 bucks for the drag link one and it does come with the U bolts and nuts to hold it on. The chassis bracket was about $60 and I used my own bolts and a magnet extension to get the bolts through the chassis. Not a difficult job, the holes all line up. Ford probably knew they would steer better with the stabilizer but didn't want to spend the extra money in assembly.
This option works and I have had great joy from driving a van with good steering.
You can find the brackets on line for 60&40 each at ford direct parts places.
Anyway thought I would share
Andrew