Hi Ralph,
I was referring to the hub and rotor only, not the spindles and sensors. I am 100% sure that the 89 and 90 have a different diameter for the step where the rotor seats on the hub. But if proven wrong, I will recant. In your junkyard tour, bear in mind that some people may have already made the changeover because the 89-90 brake rotors were rare and expensive. If my car ends up in the junkyard, you will find 91 rotors and hubs on it! (Seriously, though, if my car ends up in the junkyard, it will probably be in a Chinese steel mill before anyone has time to figure out what year the rotors are from.)