I'll contribute this, could be helpful......
I'm running a 2005 E350 extended body, former wheel chair lift equipped people hauler, 2WD with for now a semi-floater rear, 3:73 rear gears. This does have the fixed raised fiberglass roof, weight is:
Front: 3,380 lbs
Rear: 5,080 lbs
GVW: 8,460 lbs
This is fully loaded, I never tow anything and weight will never be too much more for any extended periods. I did have an extra leaf added to the stock rear springs and soon I'll have a full floating rear axle under this van.
I did use the Hellwig front & rear sway bars meant for what they call a "short wheelbase motorhome" Very large diameter, at least 25% bigger than the usual Hellwig parts called for on standard 2WD E250/350.
Bilstein shocks with the same rating, "short wheel base motorhome". With my current weight bias that combo is just about perfect---I'm almost scared to think what I'd experience with using anything "lighter" duty.
IMHO this nonsense about "comfort" vs "heavy duty" is foolish as almost certainly you'd NOT notice any ride improvement with the "comfort" rated shocks. Additionally who buys and E-Series and outfits it to the gills and expects or hopes for a sofa-on-wheels experience?
In anyone is interested in part numbers I've used I'm glad to share them--if not carry on as before!