The diff casing comes in at around £250, then you've got a 'fitting kit', so to speak, which is just bolts/shims/etc., not expensive.. then you've got your choice of differential, anything from £100 to say £400 depending on what you go for.. open, lsd, detroit locker, torsen, plate - so much to choose from in a wide range of ratios!

I worked it out at around a grand, delivered with import duties for a built differential.. there's a few guys on svtperformance.com that will build you one to your spec.. (check the 02/03 cobra forum)..

And i'd say a couple o'hundred here for custom driveshafts (you can buy the mustang couplings etc. from teh states cheaply).. and really i cant see more than a few hundred quid in fabrication work - from what I saw it was only the diff case mounts that needed modifying, it looked as if it would actually fit in the beam ok (i haven't tried though so don't assume it will)..

Those Jag conversions are about £3k aren't they? I reckon you could do the Ford 8.8 conversion for the same or less and it's an official 'ford racing' part, if that means anything