I had this conversion on my rs turbo
It was an excellent conversion.
The discs are about £80 from Ford when I bought them.
I'm sure you can pick up a set of calipers from a breakers for not that much

You need 12 - 13mm spacers and the bolts are bigger that mount the calipers.

Sure you need to drill your hubs out to 12mm

I got mine from Gadget off of here but that was a very long time ago