I didn't read through the replies, but will share that our 2007 E350 had the same wandering front end. We got a wheel alignment done while the rig was loaded up as if on a trip, including the fresh water and fuel tank being full, waste tanks empty, and all gear etc. inside. I even placed some exercise weights just behind the driver and passenger seats to simulate people sitting in the rig. With the load simulated as would be so on trips, the wheel alignment will be adjusted to the true in-use condition.
Adding heavy duty shocks, front & rear stabilizer bars, steering stabilizer, and rear trac bar, all helped to achieve a great handling rig. It went from a drunken sailor to a tight SUV feel. Getting it all done at once at a specialty truck suspension shop wasn't cheap, but oh so worth that $3900. Since 2007, we all here have learned of lower cost suppliers for the same upgrades, and Do-It-Yourself means to achieve the same goals at half the cost.