Would there be more benefit to installing heavy duty sway bars first?
Everyone I talked to having an E350/E450 chassis says they do benefit from beefed up sway bars. And since you put them on the front and rear, then they should help on both ends.
I am gonna install them on my rig, as soon as I can get done with the dinghy installation. In fact I talked to the shop that will do my levelers (assuming I am going to buy them). While they don't normally install sway bars as they are usually too busy this time of year, they did say that if they install my levelers in the January time frame - which is a slow time for them - they might agree to install the sway bars for 1hr or so labor charge.
The sway bars seem to be easy enough to install yourself, but I don't have the room to do the job.
These two videos are from a guy that installed them on his Class C.