Easiest job on the planet to get mk3 speedo out... take out light switch and bit of trim next the dash to the left as well. light switch needs unlocking - use flat item and slide the lock bar open (insert between lower edge of switch box and trim), other cover trim just unclips.
then undo 2 screws that hold in frame. if you have adjustable steering column push it down fully. then take frame out, 2 more screws hold speedo cluster. undo, pull forward, unplug and its out.