Here is a thread to check out.

http://talk.newagtalk.com/forums/thread-view.asp?tid=52017&posts=7&highlight=corn%20head&highlightmode=1#M365829

You can also search for "IH corn head" "CIH corn head" "corn head" and so on and you will get lots of good reading.

 Don't be afraid of a 800 IH. All of the parts you need to rebuild it can be had from aftermarket suppliers (Shoup/Calmer/Clarke Machine). Here is a reply I had previously on rebuilding an 800.

http://talk.newagtalk.com/forums/thread-view.asp?tid=76138&mid=544347#M544347