Here are the changes I made on my E450:
1. Got a good alignment
2. Installed bigger swaybars (Hellwig) front and rear
3. Installed Saf-T-Plus steering controller
I'm pretty happy with the way it drives now. My next suspension upgrade will probably be Bilstein HD shocks.
My big 32 ft. class C is very heavy at the rear, so I think it could use some sort of helper springs or extra leaf in the leaf springs. I don't think it needs any more spring rate up front, and the bigger front swaybar provides extra dynamic spring rate, so adding Sumo springs up front doesn't make sense to me, at least not for my rig. They would probably be helpful at the rear though.
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