this is much of it, but...

there was an interval where the post CPSC changes pushed on to measure the overall spindle dimension.

the post CPSC drive side arm required a longer overall length. use a spindle from the before times, and the chainline will be off, too far toward centerline.

the early pre CPSC arms - bigger ant hill on the back of the arm, use a 112-113 mm overall spindle.

the Post CPSC arms - shallower bulge, 115mm +/-.

too bad Campagnolo did not mark stuff with more detail.