We've had pretty-much the same setup as you, on our 2007 E350 chassis motor home for 10 years now. All in combination, the upgrades really did do wonders for handling. Here is what we had installed back in 2007.
- Roadmaster front and rear heavy duty stabilizer bars
- adjustable Koni RV shocks set to max load (red colored, not gold colored FSD)
- Safe-T-Plus steering stabilizer
- Henderson rear trac bar (because we tow)
I agree that the original Ford steering stabilizer is a decoration.
Here are some interesting facts about the E-series cut-away 2007 and older......
- The original shock absorbers are the same ones Ford installed on their standard E250 van.
- The front stabilizer bar is the same one installed on the E150 van.
- The E350 cut-away chassis never had a rear stabilizer bar to begin with.
What does that tell you? Ford really fell short in those areas, hence the reason for the need to upgrade.