I've researched and spoken to NW Quad Van (John), UJointOffRoad (Chris) and Quigley (Doug).
Please understand all I was interested in was the 2WD Front Axle and Brakes that come OFF 2WD E350 DRW and E450 DRW being retrofitted TO 4x4. Not the 4x4 stuff itself. That said,
I thought all would convert
NW and Quigley conversions can be sold as new through Ford with full warranty
UJoint will convert for what I'll call "traction" meaning be able to run in sand, snow, etc. That as opposed to the monster truck/rock crawling shown on their webpage. Chris' work wouldn't preserve OEM warranty.
From what I can tell, from what I've heard, Quigley is fine for "traction."
UJoint didn't have an axle off a DRW to sell me. I might have gone with Chris since he was in driving range to go get the parts.
NW had the parts but cross country shipping was crazy prohibitive.
Quigley had the parts, was totally cooperative. Packed my "kit" up in a palletized carton and had it available for my shipper on time. Carton got from PA to FL in about a day and a half. Weighed 400 pounds, shipper forklifted it onto my pickup truck for free at their terminal. I'd expect a full 4x4 Kit to weigh twice that.