iron GN 1 heads?

[87GN 98GTP]

ok heres the story, i bought this highly moded 87gn, it has gn1 heads fully done up, had a leak took off the heads. So the guy going over the heads had this ? if anyone has any insight please let me know
"Has anyone had problems with cutting exhaust valve seat in?(i.e. going into water)
has anyone has an issue with running non-hardened seats with unleaded or leaded fuel?
thanks