The scanner block is the tallest at ~2.2". You'll probably need more space though (at least 3" to be safe) because the connectors for the scanners tend to jut out above the scanner bock. Best to wait until you have it assembled the way you like it first.
i didn't get it yet...I have awhile before im going to need it. only once i see how much room the shock mounted aluminum plate + Scanner block takes up will i know how tall it will need it to be.