Clunk coming from above headliner?

[biggiefl]

I have a 83 300D and when I hit a bump(like a big tar strip) I get a pretty good clunck from above behind the sunroof. What is up there that could come loose? I really don't want to remove headliner if nothing is going to fall on my head and kill me. Interior is pretty mint and would like to leave it original. Sunroof works great and no leaks as well.