63-70 versus 71-72 Drop Spindle Differences

[mahanian]

I'm sure this question has been asked a few times before but I couldn't find the answer when I searched so I figured I'd ask it again. When ordering drop spindles, what is the difference between the ones made for 63-70 trucks and the ones for 71-72 trucks? I know they both use 71-72 disc brakes, but I vaguely remember there being a difference in the control arm ball joints? Is that the only difference? Is one preferred over the other? Do both spindles push the wheel out 3/4" per side?

I have a 72 donor truck and if it's worth the hassle I can swap the control arms onto my 67. I bought the 63-70 Western Chassis drop spindles with the upgraded 73-87 tie rod parts, but I could sell them and get the 71-72 if there is an added benefit.

Thanks in advance!