Right I have bought my alternator which has a 5 grove pulley but the duratec crank pulley and tensioner has a 6 grove pulley. Now do I need to change the alternator pulley or can I just run with a 5 grove belt??

You can use the five groove belt. I do on mine.

I changed mine to a 6 groove pulley and fitted one of these link

If I could have got one for that money when I built mine I would have gone with a 6

Run a 5, it'll be fine.

Cheers for that guys!!!