as others have said atlas all the way and definitely a 48.52 casing (baby) for a unarched mk2
i currently have a narrow 50" on mine with tarmac arches and 9j wheels
definitely go either zf motorsport lsd or a 3j nxg at the very least
cwp ratio id go with a 3.44 for a 400hp car.
all the advice others have given above is bang on the money
and definetly go 2 piece shafts 18t squires shafts in mine and took a beating definitely go to R.A.C.E (rally and competition equipment) stoke on trent for your gear.
some info for you here
http://www.classicfordmag.co.uk/wp-c...assic-ford.pdf