Difference between stock lower control arms 1984-1999 and 2000-2001

I was looking through the parts catalogs and found that MOOG lists two different part numbers for lower control arms. CK660203 is for 1984-1999 and CK660204 is for 2000-2001. Does anyone know if the part number difference is because of the switch from HP to LP axles and the length is different? Or is it something else?

The only thing I know of is a change in the bushing formula.

Now you've got me curious. Are the newer ones stiffer or softer?

I was at the parts store and put them side by side. The bushings are the same size OD but clearly different. I suspect the newer ones are softer. The lengths are identical.