The wiring makes no difference, as it's only the engine loom you will be interested in, Cosworth's are merely Ghia trim, it's not essential.

Yes the rear suspension on Estates is different, the shocks are "Concentric" but I am not sure if you can transfer over the conventional beam etc?

Also I am pretty sure the MK2 tunnels were all the same size, I seem to recall on the MK1 it can be an issue as only 1985 onward cars (IIRC) had the larger tunnel (Which would be when the Cosworth was conceived anyway)

Yes agree with the front, fit everything from a 2WD Cosworth, remember the cross member is unique as well!

Martin