Mine is a slicktop, there's a pic of the headliner in my build thread here:
http://www.1addicts.com/forums/showthread.php?t=1190719
I recall the sunroof cassette is about 2 inches tall in an e36, the e82 should be quite similar. You could likely measure the distance by putting a yard stick across the car against the top of the window opening then measure up from the center of the yard stick and compare.