As above, the 9 inch knuckle does use the smaller upper ball joint. It makes no sense to me that Mopar would have had 3 different front brake designs on the same vehicle at the same time. It would have much cheaper to just equip all models with discs. AR Engineering offers a kit to mount 4 piston 2nd gen VIPER aluminum calipers to the 10 inch knuckle... might be worth a look....