1st i recently replaced my guage faces and after reinstall of cluster my speedo is approx. 7 mph off on the slow side. Is there a fix?

2nd my timing belt w/ engine off is fairly loose on the exhaust side. Then at idle belt vibrates and sounds to posibly be rubbing belt cover or is just vibration noise. It looks like a guitar string being strummed 1.5" -1.75". This isnt normal is it? Thanks for you replys.