It's really a total crap shoot... The FWC folks seem to swear by Boise Spring in Idaho. I also had 2 bogus sets from them as well, one came stock height, one came so arched i couldn't even bolt them up. I posted the pics of them are somewhere on the FWC owners group FB page, you'll laugh when you see them. THEY HAD ONE JOB!!!
I do almost all my own work. Swapping out leaf springs is a chore and a PITA, its quite rage inducing when companies crap dont work
My magic sauce ended up being 2.5" Old Man Emu Dakar packs with 2 OME add a leafs per pack. Rode amazing, flex well, and handled the load perfectly without bags. Everyone that drove my truck commented on it.
Leaf springs are voodoo science, and require a lot of trial and error. The chances you get a custom pack for a custom truck that work well from the get go is close to nill.
FWIW, i've heard several folks having good luck with National and Atlas recently. I have no personal experience with either.
I think bringing the truck to said place doing the springs is a must do requirement. Doing it all mail order is brain damagingly frustrating when it dont work