70 Disc vs 73 disc

IIRC,there is a difference between lower ball joint shaft diameters & taper. Did this swap 20 years ago,on my 67 notch Cuda. I got lucky,and found a set of shims locally,to make the difference. If I am not mistaken,Dr. Diff was selling them now. Or swap ,to the 73 lower control arm. Either way,73 calipers are so much cheaper,than the Kelsey Hayes 4 piston stuff.