I'm thinking of asking if a bloke near me wants to sell his Sierra estate 4x4.
Does anyone know the ratio of the diff and is it LSD (as it's 4x4 I was guessing it was) Would the ratio suit ZX9r engine
Is this a suitable doner vehicle being estate are there any complications with the doner parts?

being 4x4, the front uprights are different and you would need to source some uprights from RWD Sierra. Other than that if you're using a bike engine/gearbox then it should be fine.

there are only two standard ratios for all the 4x4 sierra's

3.92 in the 2.0 DOHC and 2.0 SOHC (pinto) ones

and the much more common 3.62 from the V6 and cossie cars

all of these will be 7" LSD's with 100mm bolt-on driveshafts and rear discs

and like nick205 says you'll need a pair of 2wd front uprights (Rally Design are selling new ones at the moment) - but you can use the front brake calipers from the 4x4
the non-cosworth 4x4's use the same brakes as the 2wd ABS models (front and back) but the front discs have a different offset so you'll need 2wd ABS discs (260mm)