Well, apparently some items and armor and books got converted over, because I have no idea how these could have got in my game:
http://oi50.tinypic.com/73kx2g.jpg
http://oi46.tinypic.com/hx7meb.jpg
http://oi45.tinypic.com/55p9ja.jpg
http://oi47.tinypic.com/24c6x51.jpg
http://oi47.tinypic.com/1zn9btj.jpg
http://oi50.tinypic.com/2ltips0.jpg
http://oi48.tinypic.com/27xnnmg.jpg
You cannot wear Vivec's ash mask, but you can wear the Telvanni Cephalopod helm. To access Morrowind items, use the console: Help (item name.) Then you can find the object ID and use additem to get it. Just search stuff. "Help Telvanni, Help Redoran, Help Vivec, etc." Anything that would be Morrowind related.
Also, the console comes up with NPC's but can't "summon" them. Dark Seducer, Hircine's Aspect, Golden Saint, Scamp, etc. Hircine shows up as some green dark elf. Mehrunes Dagon shows up as a Dremora. Dark Seducers show up as invisible dremoras. Scamps show up as werewolfs. Lolwut?
Well, I knew about the books and misc items, but I had no idea that there was some armor that got converted as well. That is cool. :D
Maybe it is just because the helms are simple enough that they don't require any other adjustments? I think that the reason you cannot wear the ash mask is that is isn't actually wearable (at least it wasn't in morrowind), so that could be an explanation.
That is also very strange about the NPC's. I don't know what to make of that one.
Cool