There are two items transferred, from separate lists, in addition to the pantaloons. One will be the armor illyich is wearing, the best option was (vanilla) Mithril Chain+3 (Ulgoth's Beard). If you're not carrying one of the other armors, he carries mail of the Dead instead. In addition, one could take from a list of talismans, including the helm of balduran, the Kaz items, and Koveras' Ring of Protection. AFAIK, you couldn't take the cloak with you. I heard some weapons may replace the sword of chaos, but I never got that to work appropriately.
Comments
Does that armor transfer to BG2, though? If it does, that's a real good reason to grab it.
http://www.forgottenwars.com/bg1/miscellany.htm