Wheel Speed Sensor Question

[TrickerZ]

I went to replace all my wheel speed sensors since all the wiring was falling apart and ordered a 4 pack. The new front sensors are shorter than the old ones and don't work. It looks like there are 2 part numbers for them - 34526756378 and 34526756379. On realoem.com they both say up to 04/2000, but it looks like 34526756378 is the longer one by looking at pictures. I'm guessing 34526756379 was supposed to say from 04/2000 since mine is built in 99. What I don't understand is it doesn't look like any of the other part numbers change, so why exactly does the sensor get shorter?