you could do a few things,, could just try get hold of standard rs turbo callipers and discs, or can do cosworth front conversion, theres a good "how to" guide at top of this section,

also just found this on eBay, you'd still need to get spacers etc for callipers (all listed in how to guide at top of this section)

http://www.ebay.co.uk/itm/Sierra-4x4...AAAOSwu-BWQJRP


all depends how far you wanna go i suppose, also some people might say to change to a bigger master cylinder/servo poss from a rs turbo or i think you can use a mk3 mondeo one but requires mods,, loads of info on this site about it though,,

cheers