K/h disc brakes lower ball joint issue

I have a set of Kelsey Hayes disc brakes . However I am having a difficult time finding the correct lower ball joints for this set up. The parts stores keep giving me the lower ball joints with 1/2” mounting holes and I need the 9/16” mounting holes. Does anyone have a correct part number and brand name to use as a reference ?
Look for a 72 duster with disc brakes. I I am not mistaken the ball joint for those brakes is unique.