Just keep in mind, when considering a Ford chassis, starting in 2008, Ford changed the front grille style to distinguish the latest chassis improvements that are implemented to this day in the 2014s.
The 2008 chassis retained the earlier dash board. The 2009 chassis has the current-day dash board.
If the Ford chassis is styled like this, it has the latest suspension. There is no guarantee you won't have handling issues. You have a better chance it will be less of an issue. If your rig does have handling issues, you'll be doing the same to it as you would an earlier Ford chassis, investing in the same upgrades..

If the Ford chassis is styled like this, then you'll have the older suspension which may need a few additional suspension upgrades compared to the newer design, pending the motor home dimensional variance and wheelbase. The good news here is that you can do something about poor handling without draining your bank account.

Just a little note on the older E350. Ford never installed a rear stabilizer bar. If you own an older chassis E350, check to see if the previous owner or RV manufacture added a rear stabilizer bar. If you don't have a rear bar, you will greatly benefit from one. Install a heavy duty Hellwig bar as a bare minimum upgrade. That one upgrade alone will significantly improve handling in cross winds, passing trucks, and winding mountain and canyon roads.