Alternator pulley

Hi - I need info on an alternator for 1.8 mk1 8v I know it needs to be 65amps and I have one of this rating for a diesel, this one has the extra 'W' terminal to feed diesel tacho - will this alternator do and what size pulley do I need??? The current pulley is 70mm from edge to edge. I have measured a friends 16v and it has a smaller alternator and a 60mm pulley. Please help clear this up if you can. Can I just use the diesel one as it is with current pulley or will this not work properly????

You could just use the diesel one. The 16V might be a 90A alternator, nice upgrade if you can get the other fittings too.....