FYI, I looked at the E-Series Caster Thread linked above. There seems to be a misunderstanding. From 1992 CHASSIS model year and forward, E-Series is still Swing Axle (Twin I Beam) but it uses Ball Joints. The Ingalls 594 bushings replace the upper ball joint collars. But 1991 and earlier Twin I Beams used Kingpins which means no ball joints to adjust.
We had a 1983 chassis that I felt had too short a wheelbase (158" on a 24-ft House). It still tracked and handled better than our 2002 with 218" WB!
I had a conversation with Eric Davis (RV Handling Specialty Shop ericsrv.com) and he confirmed that Ford took a step backward with the "newer" front end. He saw the late model front sway bar (poked into the axles instead of with End Links) as much of the problem.
All I ever did on our '83 E350 was:
1. Replace Steering Box - Was Loose then Leaked after Adjusting
2. Replace Axle-to-Cross Member "Swing Bushings"
3. Replace Axle-to-Frame Rail "Radius Bushings"
4. Set Toe to about 1/8" IN
Tracked well and Steering Wheel had a good Feel and Return to Center