Does Skjor's dead body ever disappear? Also does Kodlaks body disapppear or was it in that ruin and does it stay there?
I wanna dead thrall one of these guys.......preferably kodlak.

I don't know if you've already discovered this regarding Skjor but after you've finished the questline

^ What she said about Skjor.

Re: Kodlak, his character is already coded as a "ghost" when you return to find him dead after the Silver Hand attack Jorrvaskr. As such it cannot be interacted with like the corpses of most other NPCs, it's impossible to loot it for instance so my guess would be that you can't really do anything with it at all. Which makes sense, because what happens to him even after death is written into the storyline.

As far as I know his body disappears from the game after it's burned in the funeral pyre over the Skyforge and what you encounter in Ysgramor's Tomb is his ghost or spirit, which also disappears off to Sovngarde once you cure it of lycanthropy