I am actually not sure that IU offers a dual degree with Classics. I'm a current MA/MLS student with IU's History Dept., and I've never met a student doing the MA/MLS with Classics (though of course that doesn't mean that they don't exist) nor does a dual degree with that program show up on the SLIS website.
I can't say I know much about their Comp Lit program, either.
Still, if you have any general questions about doing a dual degree with them, feel free to send me a message and I'll see if I can be of any help.