You should just get the discs and pads for a 2wd Cosworth. The 2wd Sapphire (4 door) and Sierra (3 door) Cosworth both use the same discs and calipers. They were produced from 1986 to 1990. The Cosworth 4x4 was introduced in 1990 and uses different discs and calipers than the 2wd.

I also like the Ferodo DS2500 pads for fast use. But for normal use I would get standard pads.