...I don't think many 587s had hardened seats if any did- pretty sure they were phased out prior to the leaded cars/trucks being phased out. What I've seen of the factory information leads me to believe hardened seats were phased in on 318s before going to 360s and didn't go to 340s. It's seemed to me so far that 587s were tapped for the smog ports and typically were plugged with weld- that's how the sets I've seen thus far have looked...
