I always selenium tone my kallitypes. From unblinkingeye: "In selenium toning, metallic silver is converted to a silver selenide, which is highly resistant to the effects of oxidizing agents."
Is it archivally equivalent to palladium or gold toning? I don't know, but I believe it's better than not toning at all. I dilute KRST 1:400 and tone for 4 minutes at 21C. If you experience slight bleaching of the high lights, increase your exposure time slightly to compensate. I've never experienced bleaching.