Thanks for all the suggestion, I forgot to mention I did replace both front shocks with Bilsteins. I had a really bad death wobble so I went through and replaced both tie rod ends at the knuckles, the drag link, kingpins, and shocks. I then put new tires on thinking that would also solve the tire cupping issues, but it hasn't. I went to an alignment shop (they only do frame pulls and alignments), but I didn't think about whether they were doing an alignment to Ford specs. Does anyone have a document that shows what it SHOULD be for a Quigley conversion? I have been holding off on doing a tire rotation since it's a dually van, but it sounds like I might have to. Here's how the tires are currently wearing:
You can tell there are high spots and low spots across the tread (cupping). There are zero vibrations on the van and steering wheel at high speeds, however there is higher than normal tire noise and at slow speeds you can feel the high and low spots.
I'm running Cooper Discoverer S/T MAXX tires.