Ball joints are required, control arm bushings are not. I run the same Howe upper ball joints. They’re expensive, but very nice. Drag is adjustable, and they’re rebuildable.
I run the 13” Cobra’s on my Duster, they work really well. But I have to say I’m still tempted by the viper kit. I know it’s mostly just because they look so damn cool, but I definitely understand even if they’re a bunch more expensive.