Any Cosworth one will do but depending on what size housing you want to use, probably the smaller .48 housing might be better as this is a better response as its smaller than a .63 housing.

As for fitting it, you need to take the cast housing complenty off so the core is showing and bolt the Cosworth housing on and spin it round to where you want it and line it up then tighten it all up.

May be better calling a tuning company to get advice off them.